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Purchasing Amateur Telescopes FAQ by Ronnie B. Kon

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
  1. What Company Makes the Best Telescopes?
  2. How do Meade and Celestron Name Their Telescopes?
  3. Comparison of Schmidt-Cassegrains
  4. What is the Best Telescope to Buy?

1. What is the single most important thing I should know before buying 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 everything 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 reasonable resolution.

2. What is the single best piece of advice to give to someone thinking 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.

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.

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