Purchasing Amateur Telescopes FAQ


Part I

by Ronnie B. Kon
ronnie@cisco.com
                    Last Updated: October 3, 1994

Copyright (c) 1992-1994, Ronnie Kon.  All rights reserved.


Questions in this FAQ:

        In Part I:

        1.  What is the single most important thing I should know before
            buying a telescope?

        2.  What is the single best piece of advice to give to someone
            thinking about buying a first telescope?

        3.  What Does All the Jargon Mean?

        4.  What Are Some Good Introductions To Amateur Astronomy?

        5.  What Will I Be Able To See?

        6.  Buying A Telescope
        6.1     What Company Makes the Best Telescopes?
        6.2     How do Meade and Celestron Name Their Telescopes?
        6.3     Comparison of Schmidt-Cassegrains
        6.4     What is the Best Telescope to Buy?



        In Part II:

        7.  Where Do I Buy My Telescope?
        7.1     What About Buying Used?
        7.2     What About Building A Telescope?

        8.  What Accessories Will I Need?

        9.  What are Digital Setting Circles?

        10. Why Should I Start With Binoculars?
        10.1    How Do I Hold Binoculars

        11. What Books and Star Charts Are Recommended?
        11.1    What About Computer Programs?
        11.1.1     What Programs Can I Get For Free?

        12. About this FAQ


Contributors to this posting include:

         Pierre Asselin  Dana Bunner     Doug Caprette
         Mike Collins    Kevin Deane     Jay Freeman
         Chuck Grant     Dyer Lytle      Christopher Gunn
         Doug McDonald   Andy Michael    Dave Nash
         Jim Van Nuland  Bill Nelson     Leigh Palmer
         Alan Peterman   Tom Randolph    David Smith
         Geoff Steer     Mario Wolczko   C. Taylor Sutherland
         Paul Zander



1.  What is the single most important thing I should know before  buy-
ing a telescope?

This is the single most important thing you should  get  out  of  this
FAQ: DO NOT BUY YOUR TELESCOPE FROM A DEPARTMENT STORE.  Ignore every-
thing any literature tells you about magnification and such.  Buy from
a  telescope  store,  where  you  will  get  a telescope that makes as
smaller claims, but will give you FAR better performance.

The reason is that as far as telescopes go, how much you  can  magnify
is  a function of the amount of light the telescope receives, which is
almost entirely determined by the telescope's aperture  (the  size  of
the  lens  or mirror that points at the sky).  As far as magnification
goes, you can expect 50x per inch of aperture on a normal night, up to
62.5x  on  an exceptionally clear night (this is the number Meade uses
in calculating their magnifications).

Department stores always show little 2 1/4 inch refractors for  up  to
300+  dollars and say that the refractor can get up to a whopping 600x
or so.  Strictly speaking, this is true.  However,  applying  the  50x
rule,  it  is  easy  to see that 125x would be pushing the optics, and
that is assuming that they were high quality ones.  With  the  quality
of  the parts they usually give you are lucky to get 100x with reason-
able resolution.

More details will follow.  I put this up at the top  so  even  if  you
read nothing else, you will read this.


2.  What is the single best piece of advice to give to someone  think-
ing about buying a first telescope?

Find a local astronomy club and attend a star  party.   Find  ways  to
look  through  telescopes  of  different quality and prices so you can
determine what you want to buy.  This FAQ can  give  you  information,
but  cannot  possibly  compare  to  actually going out and looking for
yourself.  Besides, it's the last chance you'll get to look at the sky
for free.




3.  What Does All the Jargon Mean?

OK, by popular request, here is a glossary of common  astronomy  terms
encountered  in amateur astronomy.  Words in bold face (or underlined)
can be found defined under their own heading.

altazimuth mount
     This is what you think of when you think of a tripod  mount.   It
     allows  movement  in  two  directions:  parallel  to  the  ground
     (azimuth), and at right angles to the ground (altitude).   It  is
     very useful for terrestrial observations, as it is a very natural
     way of observing.  It is significantly less useful for astronomi-
     cal use, where an equatorial mount is preferred.

aperture
     The diameter of the objective.

Barlow
     A Barlow lens is a device which has the effect of increasing  the
     magnification.   It  does this by lengthening the effective focal
     length of the telescope you are using.  Thus  a  2x  Barlow  will
     double  the  magnification, a 3x will triple it.  Barlows used to
     have a bad reputation, stemming largely from rather poor  quality
     ones  being  sold.   Modern  Barlows  are high quality and a good
     choice for expanding your collection of  eyepieces.   You  should
     keep the Barlow in mind when buying eyepieces--buying a 3mm, 6mm,
     12mm, and a 24mm and a 2x Barlow is a very dumb idea.   The  only
     use you get from the Barlow is changing the 3mm to a 1.5mm (which
     is probably going to give you higher  than  usable  magnification
     anyway).   On  the other hand, a 6mm, 9mm, 15mm and 24mm would be
     complemented very well by a 2x Barlow.

catadioptric
     Any of a number of compromise telescope  designs,  using  both  a
     lens  and  mirrors.   Examples  are  the  Schmidt-Cassegrain  and
     Maksutov-Cassegrain.  Because the light path is folded twice, the
     telescope is very compact.  These are pretty expensive.  Pictures
     can be seen in the ads in any issue of a popular astronomy  maga-
     zine:  the  Meade  2080  and  the  Celestron  C-8 are examples of
     Schmidt-Cassegrain; the Celestron C-90 and Questar  are  examples
     of Maksutov-Cassegrain.

chromatic aberration
     In refractor telescopes, which use lenses to bend the light, dif-
     ferent wavelengths of light bend at different angles.  This means
     that the stars you see  will  usually  have  a  blue/violet  ring
     around  them,  as  this  light  is bent more than the rest of the
     spectrum.  It is not present at all in  reflectors,  nor  to  any
     significant  degree in catadioptrics.  Different glasses and cry-
     stals (notably fluorite) are sometimes used to compensate for the
     aberration.   Such  telescopes  are  termed  "achromat," or "apo-
     chromat" if the correction is is nearly perfect.

collimation
     This refers to how correctly the optics are pointing towards each
     other.  If a telescope is out of collimation, you will not get as
     clear an image as you should.  Refractors generally  haved  fixed
     optics,  so  you  don't  have  to collimate them.  Reflectors and
     catadioptrics usually have screws that  you  turn  to  collimate.
     (This only takes a few minutes to do--it is dead easy).

coma This refers to the blurring of objects at the edge of  the  field
     of  view,  most  common in short focal ratio Newtonian telescopes
     (at f/10 and longer,  Newtonians  are  very  well  corrected  for
     coma).

declination
     All astronomical objects are located via a pair  of  coordinates:
     Right  Ascension and Declination.  These are easily visualized by
     imagining that the Earth is in the center of a  hollow  celestial
     sphere,  which has all the stars, nebulae and galaxies painted on
     the shell, and the sun, moon and planets move around the  shell's
     inner surface.  We can then project the Earth's lines of Latitude
     and Longitude onto the sphere, and have  a  unique  location  for
     each  object  (obviously,  these  will change rapidly for quickly
     moving objects, very slowly for slower objects.  See also preces-
     sion).   The  Declination  is  the  celestial latitude, the Right
     Ascension is the celestial longitude.  "The Ecliptic" is the path
     the  Sun  travels  over  the course of the year.  If it were pro-
     jected onto the Earth it would form a sine wave  bounded  by  the
     Tropics of Cancer and Capricorn.

Dobsonian
     Named for John Dobson of The San Francisco  Sidewalk  Astronomers
     (who  prefers  to  call  these  "Sidewalk Telescopes"), this is a
     design which allows for very large apertures at  very  affordable
     prices.   The  trade-off  is  that they are mounted on altazimuth
     mounts, instead of equatorial ones, which makes them  essentially
     useless  for  astrophotography, but an inexpensive alternative if
     you only plan to do visual work.  These are  light  buckets.   If
     you  are  planning to build your own telescope, you might want to
     consider a Dobsonian.

double star
     A double star is a pair of stars which appear to  be  very  close
     together.   There  are  two  types of double stars: binary stars,
     where the two stars are actually a part of  a  system  and  orbit
     each  other;  and  optical  doubles,  where the two stars are not
     gravitationally bound at all, they just happen to lie on the same
     line of sight from the Earth.

ephemeris
     Plural, ephemerides.  A table of  the  location  of  a  celestial
     object at regular intervals in time.

equatorial
     An equatorial mount is set to the current latitude, and is  polar
     aligned  (pointed  at  the North Pole in the Northern Hemisphere,
     the South Pole in the Southern Hemisphere) and then moves only in
     Right  Ascension  and  in  Declination.  This take a while to get
     used to, but offers the wonderful side effect of  being  able  to
     track  the  astronomical  objects you are looking at as they move
     across the sky (which is very visible motion at  telescopic  mag-
     nifications)  by  moving in only one direction (Right Ascension).
     Most equatorial mounts come with motor drives that take  care  of
     this for you.

exit pupil
     This refers to how wide the beam of light  exiting  the  eyepiece
     is,  and  is  equal to the aperture divided by the magnification.
     If it is bigger than the size of your pupil in the dark (7mm when
     you  are young, 5 or 6mm when you are over 40, as a general rule)
     you will not be taking in all the  light  available--effectively,
     you will be using a smaller aperture telescope than you have.

eyepiece
     This is the thing you actually look into.  Almost all  telescopes
     separate  the  Optical  Tube (the telescope proper) from the eye-
     piece.  Essentially, the telescope makes a really tiny  image  of
     what it's pointed at.  The eyepiece acts as a magnifying glass to
     allow you to see the image bigger than  it  would  otherwise  be.
     The magnification is the focal length of the telescope divided by
     the focal length of the eyepiece.  Eyepieces are described by the
     diameter  of the barrel, always expressed in inches (.965", 1.25"
     and 2" are the sizes in common use) and the focal  length  always
     expressed  in millimeters (4mm - 40mm is the usual range).  Short
     focal length eyepieces are also termed  high  power,  long  focal
     length are low power.

     Also significant with eyepieces is the  apparent  field  of  view
     (expressed in degrees) and eye relief (expressed in millimeters).
     The apparent field refers to how big the circle of space you  see
     in an eyepiece appears.  Bigger is better.  Eye relief is a meas-
     ure of how far from the eyepiece you can have your eye and  still
     see.   If  you wear glasses to correct astigmatism, you will need
     fairly long eye relief (the focus knob will  correct  for  almost
     all vision problems except astigmatism).

     There are several types of eyepiece designs.   The  most  popular
     are  Kellner  (inexpensive,  most  popular  for cheap telescopes,
     short eye relief and narrow fields of view.  Good to avoid if you
     can  afford better); Orthoscopic (good price/performance comprom-
     ise); Erfle (wide field of view, expensive); Plossl (perhaps  the
     best  all-around  eyepiece.   Some  moderately expensive versions
     available); and Ultra Wide (very  expensive,  almost  double  the
     number  of  lenses  as other designs makes for more light loss in
     the eyepiece, large exit pupils.  Can  cost  more  than  a  small
     telescope.   Not  a  good  place to spend your money when you are
     just starting out).

     You really don't want to buy many .965" eyepieces--they are  gen-
     erally  not  as  well  made  as  the 1.25" ones, and if you get a
     bigger telescope it will probably  not  accept  your  .965"  eye-
     pieces.   You  can  buy  an  adapter to let you use 1.25" in your
     .965" focuser.  This is probably worth the money.

f/10, f/6.3
     See Focal Ratio

finder scope
     The finder scope is a low power telescope attached to  the  tele-
     scope  you  are using.  Because most telescopes show such a small
     portion of the sky, it is virtually impossible to locate anything
     just  by  looking  through  them.  So you look through the finder
     scope to center the object you want (the finder  has  crosshairs)
     and  then  you  can use your real telescope on it.  Note that you
     can ignore all the claims about big finder  scopes.   You  almost
     certainly  don't  care.  All you need is to be able to point your
     main telescope at something in the sky.  Finder scope  size  only
     matters  when you are starhopping through fairly dim stars (where
     the larger aperture allows you to see dimmer stars).   This  will
     not be an issue for you for quite a while (if ever).  Many people
     use a Telrad sight, which is simply a red LED you can sight  on--
     you  get  absolutely  no  more aperture than your naked eye.  The
     finder scopes are usually advertised  as  8x50  (or  such).   The
     eight  refers  to  the  magnification,  the 50 to the aperture in
     millimeters--just like binoculars.

focal length
     This is the length of the light path, from the objective  to  the
     focal  plane.  The magnification is the focal length of the tele-
     scope divided by the focal length  of  the  eyepiece.   See  also
     focal ratio.

focal plane
     The plane that the telescope (or eyepiece) focuses on.  When  you
     turn the focus knob on the telescope, you are moving the eyepiece
     back and forth until you make the two focal planes coincide.

focal ratio
     Also referred to as the "speed" of the telescope, is the ratio of
     focal  length  to  aperture,  and  is  always  expressed as an f/
     number.  Thus an 8" telescope with a 2000mm focal length is  f/10
     (because 8" is 200mm, and 2000 / 200 = 10).  An f/10 telescope is
     "slower" than an f/4.

     Fast telescopes give wider, brighter images with a given eyepiece
     than  slower  ones  (but  note that at a given magnification, the
     images are--assuming identical optics--exactly the same: what you
     see  through  a f/6.3 telescope with a 12mm eyepiece is identical
     in width and brightness to what you  would  see  through  a  f/10
     telescope with a 19mm eyepiece).

     In general, the slower the telescope the more forgiving it is  of
     optical  errors  in  the  objective and eyepiece.  A telescope of
     f/10 is fairly forgiving, f/6.3 much less so.
focuser
     This is the thing that holds the eyepiece.  It moves in  and  out
     so  you  can focus the telescope.  It is always included with the
     telescope when you buy one.  The size, almost always .965", 1.25"
     or 2" refers to the barrel diameter of the eyepieces it accepts.

fork mount
     A fork mount is a type of mount where the telescope  is  held  by
     two  arms,  and  swings between them.  A fork mount can be either
     alt-azimuth or equatorial (through the use  of  a  wedge).   Fork
     mounts are most commonly used with Schmidt-Cassegrain telescopes,
     and are almost always equatorial.

German Equatorial Mount
     The first equatorial mount devised and still the most common  for
     small  to  moderate  sized reflectors and refractors.  Unlike the
     equatorial fork, the german equatorial is suitable for telescopes
     with  either short or long tubes (although, if poorly designed, a
     long tube may strike the tripod, preventing viewing at  the  zen-
     ith).   They  usually  are  designed with movable counterweights,
     which make them easy to balance, but heavy and bulky.

     The tube of the telescope is joined to a shaft  (the  Declination
     shaft  or axis) which rotates in a housing that in turn is joined
     at right angles to another shaft (The  polar  axis).   The  polar
     axis  is pointed at the celestial pole (just like any other equa-
     torial mount).  A counterweight, which is required  for  balance,
     is placed on the other end of the decination shaft.

     Tracking an object past the zenith requires that the telescope be
     turned  (both Right Ascension and Declination rotated through 180
     degrees), which reverses the field of view.  Not so much a  prob-
     lem for visual astronomy, but a limitation on astrophotography.

light bucket
     A common slang term for a large aperture.  The cure for "Aperture
     Fever."   Well,  not  really.   After a month with the Keck tele-
     scope, any amateur worth her salt would  be  bitching  about  how
     much more she could see if only she could double the aperture.

Maksutov-Cassegrain
     See catadioptric.

meridian
     An imaginary north/south line passing through the zenith.

nebula
     Plural nebulae.  An unfortunate term which basically means "some-
     thing  up there which isn't a star or a planet."  Until the early
     years of this century nobody knew what the diffuse light  sources
     in  the sky were, so they were all termed nebulae, from the Latin
     for mist.  They encompass galaxies, supernova remnants and  space
     dust.   "Emission  nebulae" are nebulae that emit light, thus you
     can see them.  "Dark nebulae" are things which don't emit  light,
     and  hence  can  only  be  seen  as  a  dark foreground against a
     brighter light.  The Horsehead Nebula is probably the most famous
     dark  nebula.   Note that most astronomers will grimace loudly if
     you refer to galaxies as nebulae.

Newtonian
     See reflector.

nutation
     Like precession, this is a term you really  don't  want  to  know
     about.   It  turns  out that not only does the sun make the Earth
     wobble in her orbit (see precession),  the  moon  does  as  well.
     This  wobble  (about  10  arc  seconds  with a period of about 18
     years) is termed nutation.  You will never have  to  worry  about
     it.

objective
     This is the thing that gathers light from the sky and  folds  the
     light into a cone.  In a refractor it is the big lens that points
     at the sky, in a reflector it is the big mirror at the bottom  of
     the  tube.   The  job  of the objective is to create a light cone
     which comes into tight focus at a single focal point.

optical tube
     This is the telescope proper.  It is the  tube  which  holds  the
     objective.   The  rest  of the stuff are accessories, such as the
     mount, tripod, and eyepieces.  When reading ads, note that  some-
     times  optical tubes are sold by themselves.  You will need to go
     out and buy (or build) a mount for them before you can use them.

precession
     This is a motion which you don't need to think about.  It is  the
     drifting  of  the north pole, and all other celestial coordinates
     with it, in a rough circle.  This occurs over so long a  timespan
     (it  is a 26,000 year cycle) that it will not affect you.  It is,
     however, one of the main reasons (proper motion being the  other)
     that star atlases are all prepared as of a specific date (January
     1, 2000 is the current standard,  the  previous  was  January  1,
     1950.   Except  they  are really December 31 of the year before--
     which makes a huge difference, as you can well imagine).

proper motion
     Everything in the Universe is moving relative to the  Earth.   It
     is  convenient to divide this motion into two vectors: the motion
     directly toward or away from the Earth  (termed  radial  motion),
     and the motion perpendicular to the former, termed proper motion.
     Motion directly towards or away from the Earth has no  effect  on
     the  body's position as seen from Earth.  Proper motion, however,
     does.  This is one  reason  (along  with  precession)  that  star
     charts are prepared as of a specific date.

reflector
     A reflector is any telescope which uses a mirror  as  its  objec-
     tive.  The most common type is the Newtonian reflector, which has
     a mirror at the bottom of a tube, which focuses the light into  a
     cone  which  is  deflected by a flat "secondary" mirror (which is
     mounted near the top of the tube in something called a  "spider")
     out a hole in the side.  This is where you put the eyepiece.  The
     advantages of the Newtonian design are numerous:  there  is  only
     one  optical surface on a mirror, as opposed to two on a lens, so
     it is cheaper to make; part of the light path is at right  angles
     to  the  length of the tube, so it can be somewhat shorter than a
     similar refractor; you can get it in much larger apertures than a
     refractor,  and there is no chromatic aberration .  The principle
     disadvantage is that you do not get as good resolution as with  a
     refractor of equal aperture (all other factors being similar).

refractor
     This is what you usually think of as a telescope--it has  a  lens
     at  one  end,  and  you look straight through the other.  This is
     sometimes referred to as a "Galilean" telescope, as it is of  the
     same  design  that  Galileo  used  (although strictly speaking, a
     Galilean telescope is a specific kind of  refractor--one  with  a
     simple  double-convex  objective lens and a simple double-concave
     eye lens.  This will not be on the quiz, so you need not memorize
     it).  See reflector for a comparison of the two designs.

right ascension
     See declination.

Schmidt-Cassegrain
     See catadioptric.

spherical aberration
     A problem where a lens or mirror in a  telescope  is  not  shaped
     correctly, so the light from the center is focused at a different
     location than the light from the edges.  You should never have to
     worry about this.  This only shows up in really cheap telescopes,
     like the Hubble Space Paperweight.  [OK, this last comment is  no
     longer  appropriate  (if  it  ever  was).  But I am leaving it in
     because it emphasizes the  similarities  between  the  telescopes
     available to you, and the very best professional telescopes.  The
     optical laws governing them are identical.]

spotting scope
     A small telescope, always a refractor or catadioptric,  generally
     used  for terrestrial viewing.  Of limited utility for astronomy,
     though many are marketed as  such.   Probably  the  wrong  choice
     unless you want to use it also for birdwatching, or as a powerful
     telephoto lens on a SLR camera.

The Starry Messenger
     The Starry Messenger (or TSM) is a classified advertising monthly
     for astronomy stuff.  Lots of ads, so a must-have for anyone con-
     sidering buying used.  It has started charging the sellers  a  4%
     commission,  though,  which has prompted a new paper, "The Cosmic
     Exchange" (TCE), to begin publishing without charging the commis-
     sion.  I expect only one of them to last.  Currently TCE is about
     half the size of TSM, but is growing.  Subscriptions are $20/year
     for TSM, $16/year for TCE.

wedge
     This is the thing that a  fork-mounted  Schmidt-Cassegrain  tele-
     scope  will  attach to, to connect it to the tripod.  You want it
     to be sturdy.

worm drive
     This is the sort of drive most telescopes come with, if they come
     with  a drive.  It is a very accurate and smooth drive.  However,
     due to imperfections in the manufacturing process, there will  be
     periodic  errors that occur at the same point in every worm cycle
     (usually about 8 minutes).  To deal with this, higher  end  tele-
     scopes  come  with  drives  which  compensate  for the mechanical
     defects.  Celestron's is the  PEC  (Periodic  Error  Correction),
     Meade's is the Smart Drive.

zenith
     The sky directly overhead.  An object "transits" when its line of
     right ascension crosses the zenith.


4.  What Are Some Good Introductions To Amateur Astronomy?

In the United States, there are two popular astronomy  magazines:  Sky
and  Telescope  (S&T), and Astronomy.  Of the two, S&T is more techni-
cal, while Astronomy has more  things  like  "artist's  conception  of
Jupiter-rise  on  Ganymede"  which  are very pretty.  I consider S&T a
necessity, but getting both is not a bad idea.

In the U.K., there is a magazine called Astronomy Now which you  prob-
ably  want to subscribe to.  It is rather like Astronomy in style, but
slightly less bulky.  Also, fewer pretty pictures.  There  is  also  a
magazine called Popular Astronomy (which is not sold on newstands--you
have to join the Junior Astronomical Society).

There is also a U.K. monthly periodical  The  Astronomer  (ISSN  0950-
138X).   This  is stapled A4 format with glossy front and back covers.
It is the journal of a group of observers of  the  same  name  and  is
devoted  to  rapid  publication of observations.  Not for the absolute
beginner.  Contact John Colls, 177 Thunder  Lane,  Norwich,  NR7  0JF,
United  Kingdom.   (+44 603-36695).  Subscriptions are 21 pounds (UK),
25 pounds (rest of Europe)>

There are many good introductory books.  I can  recommend  The  Light-
Hearted  Astronomer  by  Ken Fulton as being an excellent introduction
for the complete neophyte.  The writing style is a little  irritating,
but  it  is full of practical information.  It is more about observing
than astronomy, though.  It has advice like "if you are in bear  coun-
try, make a lot of noise so the bears don't bother you."

P. Clay Sherrod's A Complete Guide  to  Amateur  Astronomy,  available
through Sky Publishing Company, is a more technical introduction.
Sidgewick's books are absolutely excellent books,  probably  the  very
best ever written on amateur astronomy.  They are also probably over a
beginner's head.  Holding off on these for a while would not be a  bad
idea.

Nightwatch by Terence Dickinson is a good introductory book on Astron-
omy.  Great section on purchasing a telescope.  Star charts are so-so.

The Backyard Astronomer's Guide by Terence Dickinson and Alan Dyer.  A
comprehensive  introduction  to  astronomy  and the equipment amateurs
like to use.  Written by and for amateur astronomers.

Also see below, the section on Books and Starcharts.


5.  What Will I Be Able To See?

The best way to find out is to go observing with someone.  Look for  a
local  astronomy  club  (S&T lists them periodically).  This is also a
very good way to get a good price on a used telescope of proven  qual-
ity.

In general, you will be able to see all planets except Pluto as disks.
You  will  be  able  to  see the bands and Red Spot on Jupiter and the
rings around Saturn.  You may be able to see  the  ice  caps  on  Mars
(although  Mars is probably the most disappointing object in the Solar
System).  Venus and Mercury will show phases but not much else.

You will be able to see four of  Jupiter's  moons  as  points.   Ditto
Saturn's moon Titan.  You will be able to see comets.

Do not expect your images to be anywhere as nice as the ones  you  see
>from   the  Voyager  spacecraft.  If a $2000 telescope could get these,
nobody would have spent billions of dollars to send a  spacecraft  out
there.

As far as "deep sky" objects, you will be able to see all the  Messier
objects in most any modern telescope.  Galaxies will tend to look like
bright blobs.  Look a while longer and you may find some  spiral  arms
or  dust  lanes  (assuming  it  has them).  Galaxies look nothing like
their pictures--you will not see the arms anywhere near as clearly.

You will also find that the colors you see are considerably more muted
than the pictures you see.  This is because our retinas work by having
two different types of light sensitive organs, rods and  cones.   Rods
are  very  sensitive  to  dim  light, but relatively useless for color
vision.  Cones are the opposite.  Thus when looking  through  a  tele-
scope you are using your rods, and you aren't seeing a lot of color.

6.  Buying A Telescope

6.1.  What Company Makes the Best Telescopes?

Hard to say, actually.  The two  biggest  sellers  are  Celestron  and
Meade, both of which turn out good quality optics at fairly affordable
prices (Celestron's optics have the reputation of  being  better  than
Meade's).   Both  do,  however,  occasionally turn out clunkers, which
they will repair for free (as long as you are the original buyer).

Televue has a very good reputation, at a somewhat higher price.  Ques-
tar has an excellent reputation, at an astronomical price.

Coulter makes inexpensive Dobsonians, with  acceptable  optics.   They
offer the most aperture for the money, with several drawbacks.  First,
they are big.  Think long and hard about how you are  going  to  tran-
sport  it  before deciding on the 10 inch or bigger.  Second, they are
basically deep-sky telescopes.  All the Odyssey Dobsonians  are  short
focal-ratio,  which  means they're picky about alignment errors.  They
all also have more than a trace of coma near the  edge  of  the  field
(minor  to unimportant nuisance for clusters, nebulae, and galaxies; a
more serious one for planets and other small targets).  Hence  they're
not  as  suited  for  high power planetary work as your basic, medium-
sized refractor.  The telescope is very basic; in particular no finder
scope and the focuser is a bit on the rudimentary side--a simple fric-
tion tube you pull in and out of the telescope's side.   Third,  they,
like  all  Dobsonians, are altazimuth mounts: very stable but unsuited
for astrophotography. Also, you usually have to  order  directly  from
Coulter  and  they're  back  ordered for six months or more on most of
their telescopes.  You  can  look  for  a  dealer  who  could  deliver
quicker, for a bit more money (like $100).

Tasco is sold at Toys R Us.  Buy some Lego Blocks while you are there,
and you can build your own tripod, and have a mount of like quality to
your optics.

6.2.  How do Meade and Celestron Name Their Telescopes?

Both in rather stupid  ways,  Celestron  being  stupider  than  Meade.
Essentially, every Celestron Telescope is C-#, where the # is the size
of the aperture in either inches or millimeters.   Thus  the  C-90  is
Celestron's  90mm  spotting  scope (a Maksutov-Cassegrain), the C-8 is
their 8" Schmidt-Cassegrain, the C-6 is their 6" Newtonian.  They will
prefix  these with "Super Polaris" to indicate the the telescope comes
with their Super Polaris  tripod  and  mount  (a  German  Equatorial).
Powerstar  or  PEC  (for Periodic Error Correction) means it has their
good drive (comparable to Meade's Smart Drive).  Ultima means it comes
with a heavier wedge and fork.

Meade simply numbers everything.  2080 means an 8" Schmidt-Cassegrain.
2120  means  a  10".   Premier  means sturdier wedge and tripod, and a
better drive (but the same optics).  All Premiers manufactured in  the
past  coupld  of years (but not necessarilly before) are equipped with
"Smart Drive," which is essentially the same as Celestron's PEC.   The
Premier  telescopes come with model numbers: 30 or 36 (no longer sold)
means no hand controller, 40 or 46 means you get the hand  controller,
50  or 56 means you get a declination drive (so the N/S buttons on the
hand controller work) along with a slightly bigger finderscope  and  a
2"  diagonal,  70  or 76 means you get a whole bunch of stuff.  If the
number ends in a 0 (eg. 40) it is f/10.  If the number  ends  in  a  6
(eg.  46)  it  is  f/6.3.  If the number has an H postfixed to it (10"
models only) it comes with the "superwedge," a heavier wedge  that  is
more  stable  than the regular wedge, and is useful for astrophotogra-
phy.  The rest of their stuff is  pretty  obvious,  if  you  stop  and
think: the DS-16 is a 16" reflector, for example.

Meade has recently introduced the LX100  and  LX200  series  of  tele-
scopes.  The LX refers to the drive (Meade has a very strange habit of
changing  what  LX  means--it  used  to  refer  to  the  drive,   then
(apparently) the focal ratio, now it's back to being the drive), which
are certainly the most wiz-bang on the market.  The LX200 has  a  com-
puter  driven declination drive, as well as the right ascension drive,
which permits it to be used without an equatorial wedge.  It can  slew
(move  quickly  across  the  sky) at the touch of a button on the hand
control, you can hit the GOTO button to go directly to one of the  747
objects  in  it's  library.   You  cannot  do  astrophotography on the
Schmidt-Cassegrains without the equatorial wedge  ($110  for  the  8",
$395 for the 10").  The LX100 does not have the declination drive, and
so comes with a wedge, and doesn't seem  to  have  most  of  the  neat
features of the LX200.

6.3.  Comparison of Schmidt-Cassegrains

One of the more frequent criticisms I have had on this FAQ is that  it
is  very  biased  towards  Schmidt-Cassegrains, and this table doesn't
help that appearance.  It is here largely because S-C's  are  packaged
in  more funny ways than reflectors or refractors, so keeping track of
the different packagings is hard.  Please bear in mind that  the  main
advantage  of  a  S-C is the smaller length for the aperture.  And you
pay dearly for that.  For a beginner, especially one who will be doing
most of her observing from her back yard, it is probably not worth the
added expense.

To make selecting a Schmidt-Cassegrain somewhat easier, the  following
table   summarizes  the  features  on  different  models.   Under  the
Make/Model column, a C indicates Celestron, a M is Meade.   The  tele-
scopes  that  come  without tripods (eg. 2045D, Classic 8, PEC-14) are
priced with their recommended tripods.  Fork is a fork mount, GEM is a
German Equatorial.

This table is very out of  date.   The  prices  are  almost  certainly
wrong,  and  some  of  the  models  may no longer be offered.  But the
equipment is most likely correct.
                                        smart   hand    DEC     motor   computer
Make/Model      Speed   Price   Mount   drive   ctrlr   drive   focus   control
-------------------------------------------------------------------------------
C SP-8          f/10    $1050   GEM     no      no      no      no      no
M 2045D (4")    f/10    $1050   fork    no      no      no      no      no
M 2080A         f/10    $1140   fork    no      no      no      no      no
C SP-8  w/SB    f/10    $1300   GEM     no      no      no      no      no
C Classic 8     f/10    $1450   fork    no      no      no      no      no
M 2120B 10"     f/10    $1600   fork    no      no      no      no      no
M LX100 8"      either  $1700   fork    yes     yes     no      no      no
C PEC-8         f/10    $1800   fork    yes     yes     no      no      no
M 2080  #40     f/10    $1850   fork    yes     yes     no      no      no
M 2080  #50     f/10    $1850   fork    yes     yes     yes     no      no
M LX200 8"      either  $2000   fork    yes     yes     yes     no      yes
M 2080  #46     f/6.3   $2000   fork    yes     yes     no      no      no
M LX200 10"     either  $2300   fork    yes     yes     yes     no      yes
C Ultima 8      f/10    $2300   fork    yes     yes     no      no      no
M 2080  #56     f/6.3   $2300   fork    yes     yes     yes     no      no
M 2120  #40     f/10    $2300   fork    yes     yes     no      no      no
M LX100 10"     either  $2400   fork    yes     yes     no      no      no
M 2120  #46     f/6.3   $2400   fork    yes     yes     no      no      no
C Compustar 8   f/10    $2800   fork    ?       yes     yes     ?       yes
M 2120  #50     f/10    ?       fork    yes     yes     yes     no      no
M 2120  #56     f/6.3   ?       fork    yes     yes     yes     no      no
M 2120  #50H    f/10    $2900   fork    yes     yes     yes     no      no
M 2120  #56H    f/6.3   $3000   fork    yes     yes     yes     no      no
C Ultima 11     f/10    $3500   fork    yes     yes     no      no      no
M 2080  #70     f/10    ?       fork    yes     yes     yes     yes     no
M 2080  #76     f/6.3   ?       fork    yes     yes     yes     yes     no
M 2120  #70     f/10    ?       fork    yes     yes     yes     yes     no
M 2120  #76     f/6.3   ?       fork    yes     yes     yes     yes     no
C PEC-14        f/11    $6500   fork    yes     yes     yes     ?       no
C Compustar 14  f/11    $9700   fork    ?       yes     yes     ?       yes

6.4.  What Is The Best Telescope To Buy?

Well, Meade has a 16" Schmidt-Cassegrain which is  beautiful.   It  is
portable  (ie.,  you  and  a couple of friends can lug it), reasonably
compact, and readily  available.   You  can  pick  one  up  for  about
$10,000.   If  you  are in a position to spend this kind of money on a
first telescope (hey Wozniak: this is the one for  you.   Buy  me  one
while  you're  at  it)  it would be a strong candidate. If money is an
object, you will have to compromise.   My  recommendations,  by  price
level,  follow.  Prices are given as a range, using the price from the
cheap New York mail order companies as a low, and Orion or Lumicon  as
a  high,  where  applicable.   Bear in mind that you will need to have
some money left over for extra eyepieces if nothing else.

You will also find useful articles  in  the  November  1991  issue  of
Astronomy  (specs  on a wide range of telescopes, and answers to a lot
of the questions about technical jargon  surrounding  advertisers  and
equipment.   There  is  also  an article in the November 1991 issue of
"Popular Astronomy." Both Astronomy and S&T (especially the former) do
review  articles  on telescopes, accessories, etc. on a fairly regular
basis.  Also, no FAQ list is going to be truly definitive--we all have
our  own  opinions  and  interests,  and  one  person's "piece-of-junk
optics" might be another person's dream telecope.  This does not apply
to department store telescope, though.  Really.

Note that this information is out of date.  I'll revise it eventually.
Almost  all the 'scopes are still available, the prices are just some-
what different.  Also, there is a line of Dobsonians from Orion  which
should definitely be included (the Deep Space Explorers).

Under $100
     Get a pair of binoculars.  The  only  telescopes  in  the  double
     digit range are pure junk.  On the other hand, you can get a good
     pair of binoculars.  Orion  sells  a  pair  (the  7x50  or  10x50
     Observer (17mm and 14mm eye relief respectively)) for $85 specif-
     ically designed for astronomy.  The Bushnell  "SportView"  are  a
     possibility as well.  If you can spend a bit more, the Orion 8x56
     Mini-Giant binoculars look like real winners ($150), with 18mm of
     eye relief.

Around $250
     Odyssey 8" ($275).  An 8" Dobsonian from Coulter  Optical.   Use-
     less for astrophotography, but far and away the most aperture for
     the money.

     The Orion 10x70 binoculars ($300).  Personally, I would recommend
     going  with  a  telescope before an expensive pair of binoculars,
     but enough people with a lot more  observing  experience  than  I
     have  have  suggested  listing  a  high end pair.  These are good
     ones.

Under $500
     The Orion SpaceProbe 4.5" Reflector ($399).   A  straight-forward
     Newtonian  on  a  German Equatorial Mount, with cable controls so
     tracking right ascension should be easy.  Most aperture  for  the
     money.   Comes  with  a tripod and a couple of Kellner 1.25" eye-
     pieces (a 25mm and a 9mm).

     The Orion Sky Explorer 80 ($533).  An 80mm equatorial  refractor.
     Fairly  sturdy tripod, and cable controls for right ascension and
     declination that should  make  it  fairly  easy  to  track  stars
     without  a  drive.   It comes with the same eyepieces as the Spa-
     ceProbe 4.5" mentioned above.

     I don't know if I'd recommend the  60mm  version  of  the  above,
     which  sells for $344.  An 80mm objective gathers 78% more light-
     -a big difference.

     Edmunds Astroscan 2001 ($290 - $340).  It is a very  portable  4"
     Newtonian  with the distinctive shape of a cylinder thrust into a
     sphere.  The sphere rests in an aluminum base and  the  telescope
     can  be pointed in any direction.  Uses 1.25" diameter eyepieces.
     Supplied with a 28mm eyepiece giving 16x and a 3-degree field  of
     view,  wide  enough  to do without a finder scope.  The drawbacks
     are that it is not very good for planets; and that it's difficult
     to  track  at  high  power.  Also the "permanent collimation" the
     Astroscan comes with probably isn't.  One respondent's  seems  to
     have  come slightly out of alignment; this is unnoticeable at low
     power (e.g., the 16x it gives with the eyepiece it  comes  with),
     but  is noticeable and rather objectionable at about 100x.  Since
     it's permanently sealed up you can't go in and tweak the  mirrors
     the way you can with most reflectors;  you have to send it off to
     Edmund so they can look at it.  Even if you could tweak it  your-
     self,  getting it all aligned would be tricky; short focal-length
     reflectors (which the Astroscan is an example of) are  much  more
     sensitive  to  minor  alignment errors than longer ones.  Accord-
     ingly, your high power images may be on the fuzzy side.

     Odyssey 10.1" ($345).  A 10.1" Dobsonian  from  Coulter  Optical.
     Useless  for astrophotography, but far and away the most aperture
     for the money.  Also the 13.1 inch ($575).  Note  that  the  13.1
     inch  appears  to be f/4.5, which means that the tube is almost 5
     feet long.  Think about how you will transport  this  before  you
     buy it.

     The Celestron C-90 Spotting Scope  with  Multi-Coatings  ($370  -
     $500).   This  is a catadioptric telescope with a 90mm objective.
     Note that due to  the  central  obstruction,  the  C-90  has  the
     equivalent  light  grasp  of  an  83mm  refractor.  The principle
     advantage is that it is compact and is very easy to carry around.
     The  disadvantage  is that it appears to be a telescope almost as
     an afterthought--the finderscope is pretty feeble, and  you  have
     to  supply your own tripod.  Probably the wrong choice unless you
     want to use it as a spotting scope in the daytime, or as a camera
     lens.   Note  that this last sentence is probably controversial--
     many people that have the C-90 rave about it.

Around $1000
     The Meade Star Finder ($760), a 10"  Newtonian.   See  review  in
     January 1993 Sky & Telescope.

     The Celestron C-6 ($720 - $900), a  6"  Newtonian.   Comes  on  a
     solid  German Equatorial Mount (the "Super Polaris"), and with an
     18mm 1.25" Orthoscopic eyepiece (42x).

     The Celestron Super Polaris C-8 with Starbright Coatings ($1150 -
     $1300).   This  is  an 8" Schmidt-Cassegrain system on the "Super
     Polaris" mount.  It comes with an equatorial mount, and  a  drive
     which  can  track  in right ascension.  Note that you do not want
     the "Classic 8," which is the same optics in a fork mount but  no
     tripod for $970 - $1250.

     The Meade 2080A ($915 - $1150).  An 8"  Schmidt-Cassegrain  in  a
     fork  mount, with a decent tripod.  Essentially comparable to the
     Super Polaris C-8.  I'd suggest buying whichever is  less  expen-
     sive.

     The Celestron SP-C102 ($1050 -  $1250).   A  4"  f/9.8  refractor
     (102mm)  on the same "Super Polaris" mount as above.  Takes 1.25"
     eyepieces (comes with a 26mm orthoscopic).

     Odyssey 17.5" ($1150).  A 17.5" Dobsonian from  Coulter  Optical.
     Useless  for astrophotography, but far and away the most aperture
     for the money.  This appears to be f/4.5, which  means  that  the
     tube  is  over  6.5 feet long.  This will not fit into many cars.
     Make sure you will be able to transport this if you don't have  a
     great observing sight at your house.

Around $1500
     The Meade 2120B (? - $1600).  The cheapest 10" Schmidt-Cassegrain
     I  could find, except for the 2120A, which appears to be the same
     'scope, but without the coatings.  The 2120A sells for $1500 from
     the  discounters, so the B is almost certainly a better buy.  The
     2120B appears to be an f/10 scope with a fork  mount.   It  comes
     with  a tripod and a motor drive in right ascension.  Presumably,
     no hand controller.  (As you may have guessed,  I've  never  seen
     one).   All in all, a stripped down 'scope, but you get the aper-
     ture, which is the most important  part  of  a  telescope  (after
     quality of optics, of course).

Around $2000
     The Meade 2120 model 40 ($2000 - $2150).   A  10"  f/10  Schmidt-
     Cassegrain  system  with "Smart Drive" and a hand controller. The
     motor works in the Right Ascension direction but not  declination
     (the  declination  motor  costs extra).  Do NOT opt for the super
     wedge.  It costs about $300 extra, and can be  bought  separately
     (ie.,  later when you decide you actually could use it) for about
     $300.  The same logic applies to all the nice things you get with
     the  model  50--it  costs  as much to buy them packaged as to buy
     them individually.  The issue is that  beginning  astronomers  do
     not  need all the fancy equipment.  The big disadvantage, which I
     did not appreciate until I bought this telescope, is  that  while
     the optical tube weighs only 45 pounds, it is unwieldy as hell in
     the case they give you.  I find that I cannot maneuver it  around
     corners  in my house, so I either have to get my wife to help me,
     or I have to carry it by holding the forks, which do not give  as
     good  a  purchase  as one would like, given that one is holding a
     $2000 piece of very sensitive, and reasonably  heavy,  junk.   It
     also  takes  up  enough room in the back of the car that it won't
     fit if we are filling the car for a camping trip.

Around $2500
     The TeleVue Genesis (? - $1600) and Systems Mount (? - $900).   A
     4" Fluorite Refractor, which many people rave about.  The Genesis
     II has been designed to fit into an airline overhead rack.

     The Meade 10" LX200.  Tons of wiz-bang features (see above),  for
     not  a  lot  more than the Premier 2120s.  The finder scope looks
     like the feeble one that came with my 2120/40, but you  can  cer-
     tainly live with that for a while.

Over $3000
     This is well beyond my knowledge.  I would recommend avoiding all
     the  fully  loaded  and  computer  controlled versions of cheaper
     telescopes available at this price level.  The fact is  that  you
     are  a beginning astronomer and don't need all the fancy junk (of
     course, this applies to the Meade LX200 also).  If you  have  the
     money,  you  should at least look at a Star Fire refractor, a JMI
     NGT reflector and a Questar.  I have heard very good things about
     all, but never seen through any.

     David Smith contributes the following about the NGT (about $9000-
     --not  an  inexpensive choice): I have spent a couple of evenings
     with an acquaintance who has an NGT-18.  It is a very good scope.
     It's comparable in size to a Dobsonian, and I don't need a ladder
     to see into the eyepiece.  I could see dim stars among  the  Tra-
     pezium which I couldn't see in other scopes nearby (4" refractors
     and 8-10" Newtonians and SC's).   The  rotating  nosepiece  works
     well,  although it places increased demands on accuracy of physi-
     cal and optical axes:  the view was sharper from one rotation  of
     the nosepiece than from another.  Disadvantages of the NGT-18 are
     price, time to set up and take down, and lack of fine adjustments
     for polar alignment.

Part II

7.  OK, Where Do I Buy My Telescope?

Well, there are three basic places:

A Store
     Yes, the obvious--you find a store (NOT a department store) which
     sells  telescopes and write a check (or, if they won't give you a
     cash discount, use a credit card that offers buyer protection, or
     gives you bonus miles, or some such).

     The advantages of this method  is  that  you  have  someplace  to
     return  the  telescope  to  if  you  have problems with it.  Some
     places even offer your money back if you change your mind  within
     some  grace  period.  The 'droids that work in the store may even
     attempt to offer some advice.  My experience is that this is usu-
     ally 100% wrong, but that's actually as useful as advice which is
     always correct, but you have to know to invert the sense.

     The disadvantage is that you generally pay more for the telescope
     itself, and you pay sales tax.



Mail Order
     There are two sorts of mail order: the discount stores that  sell
     all  sorts  of  stuff through the mail, and telescope stores that
     sell through the mail in addition to selling from their store.

     The advantages and disadvantages of mail order are  obvious:  you
     cannot  take the merchandise back easily if something goes wrong,
     but it's cheaper (and you probably pay no sales tax).



Other People
     You can find some great deals in used  telescopes.   Many  people
     buy  expensive telescopes, use them two or three times, get bored
     and sell them.  The advantage is strictly monetary: you pay  sig-
     nificantly less (and, of course, no tax).

     The disadvantage is that you are buying something "as  is"--which
     you  may  want  to  think  twice about doing if you are buying an
     expensive telescope.  Also, both Meade and Celestron offer  (lim-
     ited)   lifetime  warranties  on  their  optics,  which  are  not
     transferable.

All that having been said, here is a list of places you can buy  tele-
scopes,  with  comments as applicable.  Note that all will sell direct
or will ship.



Orion Telescopes
P.O. Box 1158
Santa Cruz, CA  95061
(also San Francisco and Cupertino)
800-447-1001
sales@oriontel.com


Orion Telescopes carries a wide selection of  binoculars,  telescopes,
and  accessories  (Celestron, Tele Vue, and their house brand; they do
not carry Meade).  They have a  30  day  "no  questions,  satisfaction
guaranteed"  refund  policy, which they do seem serious about.  A fair
number of people (myself included) have bought at Orion  and  all  are
very  satisfied  with the way they were treated.  This place is fairly
expensive, and they have the unfortunate policy of charging a  "stock-
ing  fee" if you buy from the store, which always seems to be the same
as the postage and handling fee for mail ordering from their catalogue
(which they will send you for free if you call them).

If you need technical assistance when you call, ask for Steve or Eric.




Lumicon
Livermore, California
(see S&T or Astronomy for Address)


This is where I ended up buying  my  telescope.   No  complaints,  but
there  really  was no opportunity for anything to go wrong: I drove up
knowing exactly what I wanted and what their price was, paid by credit
card, and drove my new telescope home.  And it is not all that impres-
sive that they had it in stock--I bought one of the most popular tele-
scopes around at the time.




Astronomics
(see S&T or Astronomy for address)
Norman, OK


Higher prices than Adorama and Focus (see below), but lower than Orion
and  Lumicon.   Enthusiastically  recommended by a couple of people on
the net.  As with all mail order, make  sure  the  shipping  price  is
included.




Pocono Mountain Optics
(formerly Wholesale Optics of Pennsylvania)
(see S&T or Astronomy for Address)


Not to be confused with Pauli's Wholesale Optical in Danbury, CT  (see
below).   Enthusiastically  recommended  by  a  few people on the net.
Owned by Glenn Jacobs who goes to most of the astronomy  get-togethers
in  the  NY-NJ-PA-CT  area so you actually meet him if you live in the
area.  Often willing to cut a package  deal  if  you  are  buying  big
ticket  items.  No problems returning things with which you are dissa-
tisfied.




Roger Tuthill
(see S&T or Astronomy for Address)


Enthusiastically recommended by a person on the net.   Not  the  least
expensive,  but top-notch service.  Roger unpacks, inspects and colli-
mates every 'scope he sells, and is very  good  about  refunding  your
money if you are dissatisfied.




University Optics
(see S&T or Astronomy for Address)


A few people have reported using University  Optics,  and  all  report
receiving good service.  I have heard no complaints.




Kenneth Novak & Co.
(see S&T or Astronomy for Address)
A couple of respondants have bought accessories  from  here,  and  are
very happy with them.




Parks Optical
(See S&T or Astronomy for Address)


A couple of people have mentioned that shipment can be pretty delayed,
but  the quality of their equipment appears to be high, and improving.
Salespeople vary from knowledgeble to bubbleheaded.




Adorama
42 West 18th Street
New York, NY  10011
orders: (800) 223-2500
info:   (212) 741-0052


Along with Focus Camera (see below), the lowest prices you will  find.
Expect  no  dealer  support,  and make sure you find out how much they
will charge for shipping before placing your order.  And pray that the
optics arrive intact.  I really would recommend that you not buy tele-
scopes from these guys.  Eyepieces and other accessories, however, are
probably worth the risk if the price difference is significant.




Focus Camera
4419-21 13th Avenue
Brooklyn, NY  11219
orders: (800) 221-0828
info:   (718) 436-1518


Refer to Adorama.  Same comments apply.




Pauli's Wholesale Optical
Danbury, CT


A fair number of people on the net  reported  having  bad  experiences
with  these  people.   The  most  common seemed to be being lured into
driving 4 or 5 hours to the  showroom  and  then  being  treated  very
rudely.  Only one person seemed even moderately happy with them.
7.1.  What About Buying Used?

Think long and hard before spending a lot of money  on  a  used  tele-
scope.   You  will not have a warranty, and you have no assurance that
the optics are in good shape.  If you decide to buy used, get  a  sub-
scription  to The Starry Messenger and/or The Cosmic Exchange and look
at their ads.  Also check your local paper for classified ads  selling
telescopes--this  is  where you will find your best deals, as they are
selling to the smallest audience.

It appears that most people  want  to  get  about  75%  of  list  when
advertising  in the astronomy rags (Starry Messenger, S&T, etc).  This
is probably not enough of a discount to make it  worthwhile.   If  you
can  find  something at 50% of list, you might want to think about it.
You certainly want to see the telescope before you buy.  A used  tele-
scope is just as good as a new one if it's been properly stored, tran-
sported and used.  A little dust on the optics is generally a sign  of
a  telescope  which  hasn't  been cleaned frequently, which is usually
better than one which has.  Get the May 1990 issue of Astronomy  maga-
zine which had an article on star testing a telescope (Test Drive Your
Telescope by Dick Suiter).  If you don't live close to the seller, try
to get someone from the net to go inspect the telescope for you.  (You
probably want to send them the money in this case and get them to ship
it  for  you.   This  is  a major imposition, please note, so you will
probably have to do some serious begging to talk anyone into  it,  but
it lessens the chance of fraud).

7.2.  What About Building A Telescope?

This section was written by Andy Michael.

We just took a rather unusual approach to getting  a  beginning  tele-
scope:  we took John Dobson's telescope building class and built an 8"
and a 12.5" reflector on Dobsonian mounts (of course).  We  went  this
way  for  a  few  reasons:  to  get large aperture for seeing deep sky
objects and higher magnification with good resolution when compared to
small  refractors  in this price range, to keep the price down, and to
soak up John's wit and wisdom.  The down side is that these telescopes
are  not suited for astro-photography (at least not without building a
different mount) but that didn't bother us.  Also they are large.  The
8"  tube  we broke into two pieces for easy portability, but the 12.5"
one will probably go on the roof rack.  These are about f/7 telescopes
so  the tube lengths are 56" and 7' respectively.  Of course, when you
build yours you can make whatever size you want.  On  the  other  hand
you can pack your clothes in them; try that with an SCT.  The cost was
about $250 for the 8" telescope, $450 for the 12.5"er plus about 24 to
30  hours of work and 16 - 24 hours of class.  It's a challenging pro-
ject but the first time you focus  on  something  with  a  mirror  you
ground is an incredible thrill.  Another benefit is that we now know a
lot about telescope design and if we ever have problems with  them  we
know how to fix them.

If you don't have access to John's (or other  peoples')  classes  then
you  can  try  building  one  by  reading his book and by watching the
video.  Our class was the first to see parts  of  the  video  and  had
great  success at finishing the telescopes fast and without needing to
correct the mirrors very much.  Coincidence?  Class consensus was no.

The book (excerpted from the order form):  "How  and  Why  to  Make  a
User-Friendly  Sidewalk  Telescope" by John Dobson with Norm Sperling.
To appreciate why Dobson makes each  factor  just  so,  learn  how  he
thinks  about  it.   His  philosophy of star-gazing perfuses his tele-
scopes and his book. The book includes the  only  detailed  biography;
wonderful  vignettes  from the Sidewalk Astronomers' many expeditions;
their own special way of describing celestial objects; and, of course,
complete  details  for  making  a  Dobsonian.   169  pages; 154 clear,
friendly line drawings; 9  photos.   Hardbound  in  plywood,  Dobson's
favorite material.  Exclusive source.  Send $39.95 + $5.00 shipping to
Everything in the Universe, 185 John Street, Oakland, CA 94611.

Rumor has it that there is a 90-minute  video  in  which  John  Dobson
shows  how  you  can build your own low-cost Dobsonian Telescope.  The
video is a complete step-by-step guide,  covering  telescopes  from  8
inches  to  16  inches in diameter.  $39.95 + $3.50 shipping.  This is
not available from the Everything in the Universe store.


8.  What Accessories Will I Need?

In addition to a telescope, you absolutely must have a mounting and  a
tripod.  You will also need a few eyepieces--a telescope with only one
eyepiece is like a piano with one key.

These accessories don't come cheap--expect to  pay  as  much  for  the
mounting  and  tripod  as  you paid for the optical tube.  For a first
telescope, you probably will want to buy an entire system--it tends to
be less expensive that way.  It is also easier.

Which eyepieces should you start with?  I'd  suggest  three  or  four,
maybe  a  30mm,  25mm,  20mm, 8mm and a 2x Barlow (which will give you
coverage of 30, 25, 20, 15, 12.5, 10, 8, and 4 mm).  Buy eyepieces  of
like  quality  to your telescope.  Putting a $300 Nagler eyepiece on a
$150 telescope is pointless (it  would  also  probably  tip  over  the
entire telescope).


9.  What Are Digital Setting Circles

This section was written by Jim Van Nuland

9.1.  What Are They?

Digital Setting Circles (DSCs) are a small special  purpose  computer,
mounted on or near a telescope.  The scope has shaft encoders attached
to sense the motion of the scope's axes, and the  computer  then  con-
verts  these motions to the position of the telescope, and displays it
(for instance)  in  Right  Ascension  (RA)  and  Declination.   An  8-
conductor  cable  runs from the computer to the encoders, with 4 wires
to each encoder.  RJ-45 telephone connectors are used at the computer.

They do NOT move the scope.  You push it by hand, and  the  DSCs  tell
you which way to move and how much.

What makes DSCs so desirable  is  that  they  work  on  alt/az-mounted
scopes;  and,  even  with equatorial mountings, it is not necessary to
polar align the mount.  (However, it's desirable to have the mount  at
least roughly polar-aligned so it follows an object.)

Additionally, most models have an internal catalog and a "guide" mode.
One selects an object (or, in some, a planet), and the DSCs tell which
way to move each axis.

They are marketed by Lumicon, Jim's Mobile, Inc., Celestron, and Orion
Telescope  Centers.   The  various  brands and models differ mostly in
their internal  catalogs  of  celestial  objects.   All  are  actually
manufactured  by  the  same company, Tangent Instruments of Palo Alto,
California, USA, who, however does not sell directly  to  individuals.
I  own the NGC-MAX from JMI, so some of my statements may not apply to
other versions.


9.2.  Must the ground board be leveled?

No.  An alt/az mount must have a fiduciary mark such that the tube can
be  placed accurately at 90 degrees to the elevation axis.  One way to
do this is to (one time only) level the ground board, then  the  tube.
Make  the mark in such a manner that it can be adjusted when something
changes.  Some models of DSCs allow an alt/az mount to be  initialized
in  a vertical position.  When starting the DSCs, the tube must be set
horizontal (or vertical), and then two stars are used to  align.   The
stars  must be at least 20 degrees apart in the sky (90 is ideal), and
the first may not be Polaris.


9.3.  How does one set up an equatorial mounting?

If the mount is known to be accurately polar aligned,  you  may  still
use  two  stars  as  mentioned above.  Or you may set the DSCs to take
advantage of the known alignment, and it will require only one object,
and no zero degree reference mark is needed.

If an equatorial mount is not polar aligned, it must have a  reference
mark  at  zero  degrees  declination, and must use the two-star setup.
For a German mount, the mark may be on either side of the scope  (tube
pointing east or west), and the DSCs set to correspond.  The mount may
be driven or undriven.  As for an alt/az mount, the stars must  be  at
least 20 degrees apart, and the first may not be Polaris.


9.4.  Do the DSCs support a Poncet platform?

Probably depends on the model.  The NGC-MAX provides telescope type ET
(equatorial  table).   It assumes that the table is carrying an alt/az
scope, and that the scope is initialized with the tube horizontal.   I
believe  that an equatorial mount could be used, but have not tried to
simulate it.


9.5.  How accurate is the device?

The position of the scope is displayed to one  minute  of  RA  and  10
minutes  of  dec.  Guide mode displays position error to 0.1 degree of
arc.  The actual accuracy depends on the care with which the alignment
was  done, the accuracy of the mounting, accuracy with which the shaft
encoders were installed, the resolution of the encoders, and a bit  of
luck.   If  the  level or zero was not set accurately, the system will
work poorly, and it should be re-started.  If star settings were  done
carelessly, one can simply re-do one or both of them.

The "luck" factor stems from the digital nature of the shaft encoders.
If  the  encoder  is  on  the verge of a step, you could be off by one
step.

The absolute theoretical resolution is three encoder  steps,  assuming
everything  else  is  perfect.   In  practice,  I get about 0.2 to 0.3
degrees, and closer near the alignment stars.  If I move  a  long  way
across  the  sky,  the  error is perhaps 0.5, but then I re-align on a
convenient nearby star.  It's not too unusual to get 0.1  if  all  has
gone especially well during alignment.  This with 4000 step encoders.

Accuracy is best between the alignment stars, and the DSCs calculate a
"warp" so as to spread out the error.  When re-aligning, only one star
sighting is needed.  The DSCs retain only  the  two  most-recent  star
settings, provided they are at least 20 degrees apart in the sky.

Some models allow alignment on ANY catalog object, which  is  helpful,
but  I  find  that accuracy is best on stars or very round objects.  I
find that planetary positions are especially  suspect.   The  computer
carries  only the date, not the hour.  (Use UT date.) I have often had
poor alignments when using planets, and do so only for  daylight  set-
ups; I re-align on stars as soon as I can find any.  Open clusters are
especially unreliable; galaxies are not much better.


9.6.  What objects are in the internal catalog?

This is the major difference between models.  All  have  a  few  dozen
named  stars,  used  especially  for initial alignment.  Some have the
planets.  The Lumicon models have  a  catalog  of  planetary  nebulae,
which is Dr. Jack Marling's specialty.

The NGC-MAX version 3.94 (July, 1992) has the planets; 28 user-defined
objects;  the  Messier catalog (including M40 and M110); the full NGC,
including the so-called "non-existent" objects; about half of  the  IC
catalog; a catalog of 951 interesting stars (multiple, red, variable);
and a list of 367 additional deep-sky objects, many of which are  very
faint.

For each object, the catalog has the position, magnitude, size (diame-
ter  or  separation),  constellation,  name  (if  any)  and/or catalog
number, and the type of object.  Some have a word or two  of  descrip-
tion.  This probably varies with the brand and model.


9.7.  May I add my own objects?  Comets, for instance?

The NGC-MAX accepts user objects, and I presume  most  other  high-end
models  do  as well.  I like to put in the Sun and Moon, so that I can
align during the day.  This must  be  done  carefully,  with  the  Sun
filter  attached.   THIS  IS  DANGEROUS, as the filter must be removed
when sighting on the Moon, and if you come back to the Sun,  you  MUST
have  first  re-attached  the  filter!   The  moon is a poor alignment
object because it has up to a degree of parallax, and it  moves  about
0.5  degrees  per hour.  But it provides a start, and it may be enough
to locate some bright stars, and re-align.


9.8.  What is "identify" mode?

Identify mode is present in the NGC-MAX, and  probably  other  models.
One  specifies  the  class of object, and the faintest magnitude, then
the DSC selects the nearest to the telescope's position.   Very  nice,
but in the Realm of Galaxies, alignment is critical and then there are
too many to be certain.  To check, read out the magnitude and descrip-
tion, and go to Guide mode and see how far away the object is.

It's especially useful in clouds, as one may point the  scope  into  a
clear  spot,  then ask what is nearby.  One must separately search for
galaxies, clusters, etc.

Identify mode runs continuously, so that, as the scope is  moved,  the
DSCs will (after a few seconds), indicate the new (or nearest) object.


9.9.  Can it replace star charts?

For comparatively easy objects, probably.  In  a  crowded  field,  no.
Some  models support the Tiron Atlas 2000 and the Uranometria 2000, by
indicating, for each object, the page on which it (the object) will be
found.   These  models  also  indicate  the chart corresponding to the
position of the scope, regardless of specific object.


9.10.  What other functions are present?

This varies heavily with model.  The NGC-MAX (here we  go  again)  has
two that have not already been discussed.

"Timer" counts up in hours, minutes, and seconds.  It can be  stopped,
reset,  and  re-started,  but  can't  be restarted without first being
reset.

"Encoder" shows the encoder positions in degrees.  If an alt/az  scope
was  pointed north when the DSC was powered up, then encoder mode will
read elevation and azimuth, if the scope is also  standing  reasonably
level.


9.11.  How is it powered?  How long does the battery last?

There is an internal 9-volt transistor battery.  The load is 18 to  40
mA  (NGC-MAX), depending on how bright the display is.  I suppose this
might depend on the model, too.  The maker claims 30 to 50 hours on an
alkaline  battery.   They  do  last a good long time.  There is a "low
battery" indicator which would turn on at  about  4.5  volts,  but  in
practice, I get "encoder error" messages before that.

Some models have a second connector (serial port) by which external  9
-  15  volts  DC  may be supplied.  This does not require the internal
battery to be removed; the two supplies are in parallel with diodes to
prevent back-circuits.  It does not recharge the internal battery.


9.12.  How accurately SHOULD the mount be constructed?

The brief answer is, as accurately as you'd like the DSCs to  operate.
For  an  equatorial  mount,  there must be little flexure; the RA axis
must be perpendicular to the dec axis, which in turn must  be  perpen-
dicular to the optical axis of the tube.

For an alt/az mount, the ground board must be rigid, the azimuth bear-
ing  surface  must be flat, dent-free and stiff; and the side bearings
must be the identical height, that is, the elevation and azimuth  axes
must  be  accurately  perpendicular.  In addition, the optical axis of
the tube must be perpendicular to the elevation axis.  There is a ter-
rible  irony  here:   the  Dobsonian mount works precisely because its
kinematically stable design does NOT require  that  it  be  accurately
constructed!


9.13.  How accurately should encoders be installed?

Again, the short answer is, as accurately as you'd like  the  DSCs  to
operate.   One can't do the job with a hand-held drill.  OTOH, careful
work with a modest lathe and drill press is  quite  sufficient,  espe-
cially  if performed by a modest machinist.  Most astronomy clubs have
such a person.

Best accuracy is obtained  with  high-resolution  encoders.   Standard
encoders  have  2048 steps per revolution, and high-res type has 4000.
One can also use gears to provide greater resolution, but see below.

If the encoder is connected directly to a shaft, the hole in the shaft
must  not  be  oversize.   It  must  be  straight,  well centered, and
parallel to the axis.  The body of the encoder must be held so that it
cannot rotate with the shaft.  If it is connected by gears, the shafts
must be parallel, and there must be no backlash.

Encoders are not especially delicate, but they do not like to be bent.
They  require  very  little  torque,  and  rotate  continuously.   The
setscrew should not deform the shaft.  The 4-wire connector should  be
looped  so  it does not pull on the encoder.  They may be mounted such
that the shaft is stationary, with the body moving, or the usual  way;
the direction is set in the DSCs' setup option.

In an alt/az mount, the azimuth encoder is typically mounted atop  the
center  bolt.   In this case, the bolt must be nicely perpendicular to
the ground board, and the comments about shaft mounting (above) apply.
If  the  rocker box has any side play, it will be nearly impossible to
avoid some runout.  This can be reduced by using a very long lever arm
to hold the body of the encoder.

Both side  bearings  must  be  round  (especially  the  one  with  the
encoder),  the center must be carefully located, and the encoder shaft
parallel to the elevation axis.  Any runout here  will  cause  serious
inaccuracies when moving across the sky.


9.14.  How accurately MUST the mount be constructed?

Please don't feel that only a million dollar  mount  can  be  equipped
with  DSCs.  My 1972 Optical Craftsman (German) mount works very well,
even with about 0.5 degrees of error  if  I  shift  the  mounting  and
return  to an object.  This was the economy model!  A machinist friend
helped me drill the holes for the encoder shafts.

I used UGMA grade 10 precision gears to step up the dec  shaft  speed.
The designer of the DSCs was amazed at that, and admitted that he used
UGMA 4 with adequate results.  I don't know how to calculate how  much
more accuracy I might be getting from my expensive gears.

My alt/az mount, crafted of wood in my shop with only hand tools, car-
ries  a  108mm  f/4  scope, and *always* puts an object in a low-power
field.  OTOH, if I re-collimate the scope, I must also re-position the
vertical mark.  I usually re-align after moving far across the sky.

If the mounting is less than perfect, it means that you will  need  to
re-align more often.  But if the mount is *really* sloppy, it probably
will not be satisfactory.


9.15.  Can I connect the DSCs to my own computer?

Yes, for some models.  The NGC-MAX, and probably others, has a  serial
port  that  may  be used with an external computer, so that the screen
shows a dynamic star map, identifies objects, etc.

But the attached computer must take over ALL functions, including  the
prompting  for  "level  me,"  pointing  at particular alignment stars,
guiding, calculating the conversions for RA and Dec,  etc.   I  under-
stand  The_Sky,  from  Software  Bisque, does all this, but I have not
seen it in use nor heard from a live user.

The port is a modular telephone connector (RJ11).  It has four  wires:
B+, data in, data out, and ground.  External to the NGC-MAX, the cable
must route DTR back to the attached computer as DSR, CD,  and/or  CTS,
as  needed by the attached computer.  The 4th wire is +Battery, a 9 to
15 volt external power supply, which does not charge the internal bat-
tery.  It is not necessary to remove the internal battery,

When the NGC-MAX is operating  in  "BBOX"  mode,  it  blanks  its  own
display, and does nothing but pass the shaft encoders' values over the
serial port.  It multiplies them by the encoder ratios (the latter set
in the NGC-MAX setup function), and scales them such that 00000 is the
position at power-on, and 32767 is just under 1 rotation.

Communication is at 9600,8,N,1.  When the NGC-MAX powers on, it  sends
a  hello  message such as "V2.94".  When the attached computer sends a
character (the sample program uses "Q" but  anything  seems  to  work)
down  the port; and the NGC-MAX replies with 13 characters of the for-
mat "+00000t+00000" where the "t" is ASCII 9, and the 00000s  are  the
two encoder values.

I don't use this facility, but I'm too curious not to have  tried  it.
I  used  my modem program to supply the computer side.  I use the NGC-
MAX whenever I'm doing general observing, and I  like  it  very  well.
But  I  don't  have  a portable computer to use with it, and don't too
much see the need.  OTOH, if I fell into a laptop, I'd surely want  to
try connecting them.


10.  Why Should I Start With Binoculars?

The quick answer is because you already have them, so you do not  have
to  spend any money.  Certainly going right out and buying the Fujinon
25x150 Astronomical Binocular ($11,000 list price) would be  a  pretty
stupid thing to do, no matter how good the binoculars are.

You should also avoid the quick-focus binoculars, as they are easy  to
de-focus as well.

The remainder of this section was written by Paul Zander.

Based on my experience, I suggest that you start with a pair  of  7x50
binoculars.   This  is  the  most popular size and hence good ones are
available from many stores, even some of the discounters.  Be sure  to
get ones that have anti-reflection coatings on the mirrors and lenses.
If you wear eyeglasses, you may be able to find binoculars  which  can
focus  without  them  (unless you have significant astigmatism).  Make
sure the image is sharp at the center and edges at the same time.

"7x" is the magnification.  Most people can hand  hold  these  without
needing  to  bother  with tripods, etc.  The "50" means 50mm (~2 inch)
objectives (aperture).  This gives light gathering ability similar  to
many  small telescopes.  Many advanced star gazers regularly use bino-
culars to either locate items to focus telescopes on, or just for  the
wider field of view.

When trying to view near the zenith, use a reclining lawn lounger: you
can  lie  back  and  support your arms on the chair, giving a steadier
view. You also will not get a crick in your neck.

You might also use a plastic pad to lie on.

10.1.  How Do I Hold Binoculars?

This section was written by Jay Freeman.

If you don't have a tripod (and tripods are sometimes a little clumsy,
and are often difficult to use when the binocular is pointing near the
zenith), it is important to know how to hold a binocular correctly  to
achieve maximum steadiness.

The way most people tend to hold a binocular is with one hand on  each
side of the middle of the body--roughly where the prisms are in a con-
ventional 7x50, say, so that the left hand is directly to the left  of
the center of gravity of the instrument and the right hand is directly
opposite it, to the right of the center of gravity.

For most people, there is a better position.   Imagine  that  you  are
holding the binocular to your eyes, with your hands positioned as just
described.  Now, slide your hands along the body  of  the  instrument,
toward  your  face,  until only your pinky and ring fingers are curled
around the back end of the binocular  body.   In  this  position,  the
binocular  feels  a  little  nose-heavy, because you are supporting it
behind its center of gravity.

Now curl each thumb up as if you were making a  fist,  and  flex  your
hands  so  that  the  second  bone  in from the tip of your thumbs are
pressed up against your cheekbones (counting the bone in the  part  of
your  thumb  where the thumbnail is, as the first bone).  This makes a
quite solid structural connection between the body of  the  binocular,
through your hands and thumbs, to your face, and markedly improves how
steadily you can hold the instrument.  Similarly, curl the  first  and
middle  fingers  of  each hand around the corresponding binocular eye-
piece, to provide a little more  structural  connection  (and  perhaps
also  some protection from stray light).  In this position, your hands
are not far from where they would be if you brought them to your  face
to block out stray reflections while peering through a store window at
night.

For most people, this position leads to markedly steadier viewing, but
if  the  binocular  is  especially  long and heavy (say, a 10x70 or an
11x80), the out-of-balance position can  be  quite  tiring.   In  that
case,  move  *one*  hand  out  to the objective end of its side of the
binocular, so that you are supporting the instrument on opposite sides
of  its center of gravity, but with some structural connection between
it and your face; namely, the other hand.  When the hand way out there
gets tired--just switch hands.

For each person, there is a limit to how heavy and / or how powerful a
binocular  can  be,  before there is no way for that person to hold it
steady enough.  I am an averaged-sized adult male in reasonable physi-
cal condition, and I find I can hold a 10x70 (Orion's) steadily enough
to use indefinitely on astronomical objects.  But I have an old Celes-
tron  11x80,  that doesn't look much bigger or heavier than the 10x70,
that I can only use for a few minutes before my arms get tired.  As  a
12-year  old  I  am sure I could have used a 7x50 indefinitely with no
problem, but at a younger age I might have had  difficulty  using  one
continuously.   Your  experience may vary with your strength, size and
condition.  Try before you buy, if at all possible.

10.2.  What Are Some Eye Relief Figures?

If you need  to  wear  eyeglasses  while  looking  through  binoculars
(presumably  you have astigmatism, but if you require many diopters of
correction you might need to as well) you  need  reasonably  good  eye
relief.  Dana Bunner contributes the following table:

      Model                     Advertised ER     Measured ER
      Bausch & Lomb 7x26 Custom       16               15
      Celestron 10x50 Pro             15               10
      Celestron 7x42 Ultima           23               19
      Celestron 7x50 Ultima           20               16
      Celestron 10x50 Ultima          19               17
      Celestron 8x56 Ultima           21               11
      Fujinon 8x40 BFL                19               17
      Fujinon 7x50 FMT-SX             23               20
      Fujinon 10x70 FMT-SX            19               17
      Minolta 7x50 Standard           18               16
      Minolta 10x50 Standard           ?                9 (FYI)
      Minolta 10x50 XL                18               16
      Nikon 8x30E Criterion           13               13
      Nikon 7x50 Windjammer           16               16
      Optolyth 10x40 Touring          13               12
      Pentax 8x24 UCF                 13                8
      Pentax 7x35 PCF                 14                9
      Pentax 7x50 PCF                 20               10
      Swift 8x25 Micron               13               11
      Zeiss 7x42 B/GA T Dialyt        19               18
      Zeiss 20x60S                     ?               14 (FYI)



11.  What Books and Star Charts Are Recommended?

If you don't know the constellations, you might want a book that  will
help  you  learn them.  A "fun" book for those just learning the stars
is The Stars, A New Way of Seeing Them by H.  Rey,  which  presents  a
non-orthodox  way  of drawing the constellations so they are easier to
visualize.

You will probably want a beginner's guide, such as the book by Sherrod
mentioned above.  Sky Publishing has some introductory materials which
would probably be as useful, which you get for free when you subscribe
to Sky and Telescope.

Petersen's Field Guide to the Stars and Planets  comes  highly  recom-
mended.   It  is very inexpensive ($13), small and handy to use at the
telescope. It has a good discussion about stars, planets, nebulae, and
galaxies; and has a very complete albeit small-scale star chart, along
with a the usual tables. It has long lists  of  deep-sky  objects  for
each area of the sky.

You will need a bigger star chart than is included in Petersen's.  Try
Sky  Atlas  2000.0, by Wil Tirion.  The field edition, which has white
stars on a black field, is probably more useful than the  desk  guide.
It  is  also printed on heavier paper, so is more resistant to dew and
the rigors of the night.  For beginners, buying Uranometria 2000.0  is
probably  a  mistake.  Yes, it is the "best" star chart, but the scale
is impossibly  small--when  the  Orion  constellation  takes  up  four
separate pages it is really hard to use for beginners.

Burnham's Celestial Handbook ($36).  This three volume set  is  billed
as  "An  Observer's  Guide to the Universe Beyond the Solar System"--a
rather all-encompassing claim, which it manages to live up to.  Infor-
mation  on  every  item of interest you can think of: galaxies, double
stars (optical and binary), variable stars, nebulae, etc.  More infor-
mation than you could use in a lifetime.  I consider this a necessity.

Sky and Telescope's 100 Best Deep Sky Objects.   About  $5,  which  is
kind  of  expensive  for a list, but it sure makes it easier to figure
out what to look at when you are just beginning.  The items are sorted
by  Right Ascension, which makes it real easy to figure out which ones
are currently up.

All the materials listed are available from:

                Sky Publishing Corporation
                P.O. Box 9111
                Belmont, MA 02178-9918 USA

Their catalog is free.


11.1.  What About Computer Programs?

There are basically two types of astronomy programs:  calculations  of
astronomical  things  and  computerized star charts.  I don't consider
either of them worth buying as a tool to help  an  observer.   On  the
other  hand,  some of them (particularly the star charts) can be a lot
of fun to play with during the day or on cloudy  nights.   Before  you
buy  any,  you should probably check out the ones available on the net
(see next section).
For a good example of the variety of  programs  which  will  calculate
things,  look  for  Zephyr  Software's  ad  in  Sky and Telescope (or,
presumably, Astronomy).  They list two pages of  programs,  for  about
$60  each,  which  can  calculate things like solar eclipses, or lunar
phases, or ephemerides, etc.  To my mind, your money would  be  better
spent on eyepieces, or a bigger telescope to begin with.

As for computerized star charts (usually $100 - $250),  these  can  be
very  nice.   Most  will  draw in the constellation lines if you like,
will let you click a mouse on an object to have  it  identified,  find
objects  by  name,  and so forth.  Also, the fact that they can scroll
the sky is much nicer than having to turn pages in  a  printed  chart.
The  fact that they can show the stars as they are tonight, as opposed
to a fixed time (such as 2000.0) is so pointless as to  be  laughable.
The  only  problem is that you will probably never be able to use your
computer at your telescope, which means that  this  is  something  you
will  use  indoors.   This strikes me as a nice recreation, but again,
you would be better served by spending the money  on  a  better  tele-
scope.

As for recommendations for programs, both Dance of the Planets ($200),
and  The Sky 4.1 ($75 - $175, depending on the size of the database of
objects) tend to get rave reviews in the magazines.  Both are only for
IBM PCs and compatibles.  The former is available from

A.R.C Science Simulation Software
P.O. Box 19558
Loveland, CO  80539
(303) 667-1168

The latter is available from

Software Bisque
912 12th St.
Suite A
Golden, CO  80401
(303) 278-4478


For the Macintosh, a program called Voyager is the  dominant  program.
David Nash comments that:

1)  It has a lot of features for the planets.The accuracy of its posi-
tions  probably  isn't  as  great  as some more dedicated program like
Dance of the Planets, but it is  more  than  sufficient  for  ordinary
observers.   And it does a lot:  in addition to the standard "plot the
planets against the stars" mode,  you  can  get  conjunction  searches
(handy  for  finding  eclipses), planets displayed with disk and phase
indicated, a "tracking" mode that plots planet positions  at  a  given
interval  (say,  steps  of  2  days or 1 month), and a bunch of little
features that come in handy, such as a  program  that  produces  those
magnitude  -  vs - time and angular size - vs. time plots that you see
in the astronomy magazines.

2)  NICE interface compared to most programs I've seen, including  Mac
programs  like  MacAstro,  but  then  again that is shareware and less
fully-featured. Each starchart has Mac-style scrollbars on  each  side
--  one for RA (or Azimuth) and one for Dec (or altitude).  This makes
navigating around the sky fast and simple -- grab the scroll bars  and
you're  off  and running.  Similar sorts of controls allow you to zoom
in on a region (down to 1 deg. x 1 deg.).   Much  more  flexible  than
The_Sky for the PC (the DOS version anyway -- I haven't tried the Win-
dows version, so this may not be an entirely fair comparison).

3)  Many options for plotting charts.  You can get them in  equatorial
(RA/Dec) or local horizon (alt/az) coordinates (or several others, but
these are the most useful).  A little counter in  one  corner  of  the
screen  tells  you  what  the  coordinates  of  the  cursor are in the
appropriate modes.   You can add coordinate grid lines, mark important
points or areas (zenith, horizon, ecliptic, etc.).

4)  Miscellaneous fun stuff: a 3-D map of the ~50 or so nearest  stars
to  the  Sun  (click on the axes to change the view), an "orrery" mode
that shows the Solar system from above, making it easy to  see  plane-
tary relationships (conjunctions, oppositions, etc)

It also has a fairly comprehensive deep-sky database.

The only really big drawbacks here are that the program is  black  and
white only, even on color Macs, and the star database is a bit limited
compared to many programs (esp. some for the PC).  There is,  however,
a new version which supports color, and adds more stars.




Brian Cuthbertson has a program HyperSKY, which he was kind enough  to
send  me  to  review.  Unfortunately, the first disk was corrupt, so I
could not load it onto my computer.  However, from the brief  instruc-
tion  list  he sent it appears to do what you would expect a computer-
ized star chart to--zoom, pan, identify objects, is  mouse-based,  and
so  on.  (Yes, I know that I don't have much here to base a review on,
but:  1) he is on the net, and I admit to a net.bias; and 2)  he  said
nice things about my FAQ and sent me a free copy of his program).

HyperSKY is available from Willman-Bell publishers (see ad in any copy
of S&T or Astronomy).

A correspondent recommends the program Distant Suns as  being  a  good
computerized star chart, that was written by Mike Smithwick, who some-
times reads this group.  If  Mike  would  care  to  contact  me,  I'll
include price and address here.  If he wants to send me a review copy,
I'll even give my opinion.

11.1.1.  What Programs Can I Get For Free?

Well, I use a program called ephem, for calculating  a  whole  lot  of
stuff (like ephemerides, phase (of moon and planets), dawn, dusk, etc.
and like it a lot.  There is a motif based upgrade,  xephem,  which  I
have not yet used.  You can pick it up from ftp.x.org or iraf.noao.edu
in contrib/xephem.  Ephem and xephem were written by Elwood Downey.

I have heard good reports  about  a  program  called  'starchart'  and
another  called  'observe', the former prints out star charts, and the
latter calculates where objects are, in a format  accepted  by  'star-
chart.'  You  definitely  want to get these before paying for anything
else.

For Macintoshen there is a free/shareware program  MacAstro  available
>from      cs.dal.ca    in    /pub/comp.archives/macastro    and    from
aix370.rrz.uni-koeln.de                                             in
/.disk2/usenet/comp.archives/sci/astro/macastro.  It will show the sky
at any time, including stars, sun, moon and  planets.   It  will  also
give  the  rising/setting  times  of  the  sun  and  the  moon.  It is
shareware, $20, written by Nicolas Mercouroff (nm@cs.brandeis.edu).


12.  About this FAQ

This FAQ is a copyright work.  You have my permission to reproduce  it
however  you  like,  as long as you don't make any money off of it and
you leave all the attributions and the copyright notices.

All the opinions are mine, and not my employer's.

If you have any questions, I will be happy to try to answer them.  But
be warned that I am not a very experienced observer.  Many many people
on the net have much much more experience than I do.

Because the FAQ is kept as an nroff file, generating diffs is  a  hard
problem.

This FAQ does not appear on news.answers, because they didn't like the
format.

No, I am not interested in having someone convert this to HTML  for  a
Mosaic  World  Wide  Web  Information Superhighway Wired Magazine type
application.  This is an  article,  and  I  want  people  to  read  it
through.

This FAQ is available via anonymous FTP from ftp.cisco.com,  in  /faq.
The  files are astro1.txt and astro2.txt for printable text; astro1.ps
and astro2.ps for postscript files.
-- 
----------------------------------------------------------------------------
Ronnie B. Kon       | "You couldn't deny that, even if you used both hands"
ronnie@cisco.com    |
(408) 526-4592      |                   -- The Red Queen                
----------------------------------------------------------------------------

1/9/95 - Robert Lentz (ralentz@ralentz.com)

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