Purchasing Amateur Telescopes FAQ
                    Slc.Dennis Bishop
                    starlord@ptw.com
                   Last Updated: 9811.01
 Copyright (c) 1998 Slc.Dennis Bishop  All rights reserved.
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|This FAQ is under construction There may be some sections |
| that are not totaly done yet.                            |
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Questions in this FAQ:

1. What is the single most important thing I should know before
   buying a telescope?
2. Recommendations for Beginners.
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    What is the Best Telescope to Buy?
7.     Where Do I Buy My Telescope?
7.1    What About Buying Used?
7.2    What About Building A Telescope?
7.3    What is the Best Mount?
7.4    Binocular 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?
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     David Knisely

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 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.

Department stores always show little 2 1/4 inch refractors from
125+ 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.

           Recommendations for Beginning Amateur Astronomers
           =================================================

    Occasionally, amateur astronomers ask for recommendations about
telescope buying, learning the sky, and so on.  Here are some thoughts.

    (Let me state credentials. I am primarily a visual observer: Over
40 years I have logged about 6000 observations of nearly 3000 objects,
and used perhaps thirty telescopes and binoculars enough to know them
well. I have made roughly ten optical surfaces to 16-inch diameter (a
sphere -- my biggest paraboloid was 8 inches). My forte is deep-sky
work; observations I am proud to include the Sculptor Dwarf Galaxy
(10x70 binocular), Maffei I and Leo II (Celestron 14), and S147 (6-inch
Maksutov). My interests led to a physics PhD, studying the interstellar
medium from a spacecraft: By training I am an astrophysicist, but I
maintain amateur status in visual wavelengths -- my thesis work was in
extreme ultraviolet.)

What to do First.
================

    First, some meta-advice. Written words do not substitute for
experience. Join an astronomy club, go to observing sessions, and try
other peoples' telescopes. You will learn a lot, and will find people
who like to discuss equipment and observing.

    To find clubs, ask at science stores, museums, planetariums, and the
like. Physics and astronomy departments of colleges may know, though
clubs aren't strictly their line. Two popular astronomy magazines,
_Astronomy_ and _Sky_&_Telescope_, publish annual directories of clubs,
stores, observatories, and such. Look for them on newsstands, or go to
a library and read back issues, or try their web pages.

    Been to a club already? Honest? Okay, you can keep reading...

Some Basic Questions.
====================

    In buying a telescope, you face bewildering, expensive choices. To
help deal with the confusion, here are some questions to ask yourself.

    (1) How much effort are you willing to put into learning the sky?
If you know the constellations, and have practiced finding things by
"star-hopping" -- using charts instead of dial-in or punch-in
coordinates -- you will be able to use a telescope cheaper, smaller,
lighter, and easier to set up than one using precise alignment or
computer control to locate objects.

    (2) How much effort are you willing to spend on your observing
skills? Seeing fine detail in celestial objects, or just seeing faint
ones at all, requires practice and special knowledge. Yet the rewards
are enormous: An experienced observer may see things with a small
telescope that a beginner will miss with one five times larger, even
with objects and sky conditions that favor both telescopes equally.

    (3) How far will you have to lug your telescope to get it from where
you keep it to where you use it, by what means, and how much effort will
you put up with to do so? Differences in size and optical design create
vast differences in telescope portability, and any telescope that you
take out and use will be far better than one that sits in the closet
because it is too heavy or too cumbersome.

    (4) Some people are into technology for its own sake, without regard
to whether it is useful or cost effective. Are you willing to pay extra
for sophisticated features, even if you don't need them? If so, fine --
lots of us like neat equipment. But if not, take care technology
enthusiasts don't sell you things you don't need.

    (5) Do you want to take photographs or CCD images of celestial
objects? "Astrophotography" is an expensive word. I am not into this
side of the hobby, but friends who are typically take several telescopes
and several years before they are satisfied, and spend lots more money
than visual observers do.

Some Realities.
==============

    With these thoughts in mind, I can make some general comments.

    (A) The most important thing in determining the optical performance
of a telescope is the diameter of the beam of light that goes into it --
its "clear aperture". Obviously, the more light, the fainter the things
you can see, but less obviously, image detail is limited by clear
aperture, via physical optics. Bigger telescopes produce sharper
images, just because they are bigger.

    There are important qualifiers. First, bad craftsmanship can make
any telescope perform poorly. Cheesy optics won't work. Fortunately,
it is not too hard to make optics of the sizes and types common in
amateur telescopes: most manufacturers routinely turn out units that are
okay. Bad ones turn up, but major manufacturers will often fix or
replace a real lemon, if you have wit to recognize that you have one,
and will to complain. (Most of us have neither; that's how some
manufacturers make money!)

    Second, different optical designs perform differently. Schmidt-
Cassegrains, Newtonian reflectors, and refractors all have good and bad
points. People who love telescopes, or sell them, will be eager to
debate the matter. However, variations are relatively minor. It is
usually adequate to assume all telescopes of given clear aperture and
given quality of optical craftsmanship have the same optical
performance: Real differences will correspond to changes in aperture of
usually no more than 10 to 20 percent. Shabby optical work will
increase that percentage enormously.

    Third, atmospheric turbulence ("seeing") limits the ability of a
telescope to show detail, and sky brightness limits its ability to show
faint objects. Poor seeing usually hits large telescopes harder than
small ones. When seeing is poor, there may be no reason to take out and
set up a big telescope. If you always observe from such conditions, you
may have no reason to buy a big telescope. Yet, even in bright sky, a
large-aperture telescope will show fainter stuff than a small one.  And
many of us have found dark-sky stable-seeing sites within a reasonable
drive of home -- from sites near San Francisco Bay, sometimes I have to
stare through the eyepiece of my Celestron 14 for several minutes before
I can tell that there is any air between me and what I am looking at.

    Notwithstanding these caveats, APERTURE WINS, and wins big. If you
buy the finest 90 mm fluorite refractor in the world, do not be
chagrined if a junior high school student shows up with a home-made
6-inch Newtonian that blows it clean out of the water: The 6-inch I made
at 13 puts my world-class 90 mm fluorite to shame. There is no contest,
and it's not because I was a master optician at 13, it is because six
inches is bigger than 90 mm, hence intrinsically better.

 (B) Hundreds of deep-sky objects are big and bright enough to show
well through apertures of two inches or so, at low magnifications.
Thus, medium sized binoculars -- 7x50 or 10x50, say ("7x50" means "7
power, 50-mm aperture") make inexpensive, highly portable, easily
operated beginner instruments. Perhaps you have one already. To use
them well, you must be willing to learn the sky enough to find things
with a hand-held instrument. And don't get one that gets too heavy to
hold steady before you are done observing.

    (C) Speaking broadly:

(C.1)    The most optical performance per unit of clear aperture comes
       from modern, high-quality refractors -- but they are outrageously
       expensive compared to other designs of the same aperture. Also,
       in sizes much above four-inch aperture, the tubes are generally
       long enough to make the whole instrument cumbersome and heavy.

(C.2)    The most optical performance per unit of portability comes
       from Schmidt-Cassegrain and Maksutov designs -- but they are
       still pretty expensive.
          There's a qualifier here:  What makes them portable are
       short, stubby tubes, but for small apertures -- say, four inches
       or less -- portability of all types is dominated by clumsiness
       of the tripod, so the portability advantage of Schmidt-
       Cassegrains and Maksutovs diminishes.

(C.3)  The most optical performance per unit of cost comes from
       Newtonians -- particularly those with Dobson mountings.
       Compared to other telescopes of the same aperture, they are
       clumsier than Schmidt-Cassegrains and Maksutovs, but not
       nearly as clumsy as refractors.

    Let me regroup that information into three questions telescope
buyers often ask:

(C.1') What gives most optical performance for a given aperture?

         Usually, a high-quality refractor.

(C.2') What gives most optical performance for a given car to carry it?

         Usually, a Schmidt-Cassegrain.

(C.3') What gives most optical performance for a given budget?

         Usually, a big Dobson.

 (D) Though costly and cumbersome, small refractors are durable and
difficult to get out of whack. Good ones make respectable beginner
instruments, particularly for beginners with extra thumbs. And a good
small refractor provides a wonderful way for an experienced observer to
embarrass folks with humungeous Newtonians who lack observing skills to
exploit them. But BEWARE of mass-marketed junk refractors, advertised
as high-power and sold in department stores.

 (E) Altazimuth mountings tend to be cheaper, lighter, less clumsy,
and more quickly set up than equatorial ones, but to use one you must be
willing to learn the sky well enough to find things without dialing in
celestial coordinates. (Computer-controlled altazimuth mounts allow use
of celestial coordinates to find things, or perhaps will look up the
coordinates for you, in an internal data base, but they are not cheap.)

 (F) There's another way to look at this material. There are variety
of ecological niches for telescopes, corresponding to different uses and
requirements. I know of seven:

 (F.1)    Big Iron: This is the giant Dobson-mounted Newtonian, or
      humungeous Schmidt-Cassegrain, that fills your garage. To
      transport it requires a small trailer, pickup truck, or panel
      van, and setting it up calls for the concerted efforts of three
      used fullbacks and a circus elephant. The ladder to climb to
      the eyepiece is so tall you need supplemental oxygen to deter
      altitude sickness. This telescope is your galaxy-gazer and
      cluster-buster supreme, and if it is well made, then when the
      seeing is good it will show detail that those condescending
      high-tech dweebs with their confounded itty-bitty seven-inch
      apochromatic refractors can only dream about.

      My "Big Iron" is a Celestron 14, with a little tiny
      single-axle cargo trailer to haul it.

 (F.2)    Largest Conveniently Portable Telescope: This is the most
      telescope that will fit easily in your regular vehicle without
      hiring a bulldozer to clean it out. What it is, depends on what
      your vehicle is -- with a ten-speed, or a subway train, you have
      a problem.  An eight- to eleven-inch Schmidt-Cassegrain is the
      right size for many people; that is one reason these telescopes
      are popular.

      I have had several Largest Conveniently Portable Telescopes,
      over the last few cars. Once I built an eight-inch Dobson
      whose key design parameter was that the tube just barely fit
      crosswise across my back seat. I used it a lot till I bought a
      smaller car. For a while, my Largest Conveniently Portable
      Telescope was a Vixen 90 mm f/9 fluorite refractor on an
      altazimuth fork or a Great Polaris German equatorial (I have
      hardware to fit both), but at present I use a six-inch f/10
      Intes Maksutov on the Great Polaris. A somewhat faster Dobson
      than my 8-inch f/5 would work equally well, and would have
      more performance for most purposes.

 (F.3)    Public Star Party 'Scope: You'll want something pretty
      portable, with the added provisos that it's nice to have a
      sidereal drive so you won't have to keep re-pointing it between
      viewers, and that it shouldn't be so expensive you worry about
      kids and idiots. Your SCT will do nicely.

         I put the Intes or the Vixen fluorite on the Great Polaris,
      but I set the tripod legs to maximum length, so the expensive
      optics are out of reach. So far, no one has slam-dunked a rock.

 (F.4)    Quick Look Scope: The idea here is to leave something all
     set up in your entrance hall, or hidden under a stack of old
     _Sky_&_Telescopes_ in the back of your car, so you will have a
     telescope on two minutes notice if a truly close comet comes
     whizzing by, or if you are too lazy to assemble one of your real
     telescopes.  Such an instrument can also double for nature
     watching or spying on the neighbors, which may be the same thing
     -- just don't tell your fellow amateur astronomers, or you will
     lose observer points.  Many people have a spotting 'scope on a
     light tripod, or perhaps a 90 mm Maksutov on one a bit heavier.

     Lately, my Quick Look 'Scope has been a 102 mm f/9.8 Vixen
     refractor with a conventional achromat, on a Vixen bent-fork
     altazimuth mount that has clutches and slow motions on both
     axes. I have a couple of smaller refractors that I sometimes
     use similarly, but since I have room to leave the 102 mm set up
     in my living room, I benefit from the extra aperture.

 (F.5)    Binocular: A good binocular is very useful, and can do
     much of the work of a 'Quick Look Scope. I have too many; ones
     I use for astronomy include the 7x35 Tasco ($29.95 at Sears)
     that I keep in my car for bird-watching (oops, lost observer
     points), an old Swift Commodore Mark II 7x50 (long out of
     production), which was one of the first binoculars I saw with
     BAK-4 prisms, and an Orion 10x50 and 10x70 with BAK-4 prisms
     and fully multicoated everything, up to but not including the
     case.  At star parties I tend to wander around with one
     dangling from my neck. I tried two, but lacked sufficient eyes.

 (F.6)    High-Tech Conversation-Stopper: This is how you put to
     shame those grass-chewing hillbilly clodstompers who have giant
     cardboard Dobsons with tubes so big that they echo. Odds are
     the seeing will never get good enough for them to demonstrate
     that a half-meter shaving mirror will blow eighteen centimeters
     of optical perfection clean out of the water, and if they start
     talking about faint galaxies you can always change the subject
     to diffraction rings and modulation transfer functions, and ask
     them to compare internal baffles and background sky brightness.
     Besides, your telescope has more knobs than all theirs put
     together, and it cost more than all theirs put together, too.

        The default choice for the High-Tech Conversation-Stopper
     these days is typically an apochromatic refractor, or some
     close approximation ("apochromat" is a precise technical term;
     not all superb refractors are apochromats, and vice-versa),
     which if well made and well baffled will deliver outstanding
     performance for its size. The apertures available suffice for
     many amateurs who have either recovered from aperture fever
     or have not yet succumbed, or who have exhausted their supply
     of fullbacks and circus elephants to set up the Big Iron.
     Few other kinds of telescopes qualify -- you're not allowed
     to have a Schiefspiegler unless you can remember how to spell
     it, and nobody wants a Yolo because people expect you to walk
     the doggie. Some folks like Questars, but not me.

     My present High-Tech Conversation-Stopper is the 90 mm
     Vixen fluorite refractor I mentioned earlier. It is not big
     enough to be as impressive as I might want, and is rather short
     on knobs, but I can talk fast enough to make up the difference.

What about accessories?
======================

    I have already said most of what you need to know about accessories,
which is that (A) aperture wins. If you are planning a telescope
budget, and eyepieces, finders, and such account for the lion's share of
your funds, sit back and think carefully about what you are about to do
-- it might be better to get a bigger telescope instead of fancy
accessories. A 10-inch telescope with a hand magnifier as an eyepiece
will give a better view of most objects than an 8-inch telescope with
the finest eyepieces in the world. Why? Because (A) aperture wins.

    Yet if you are up against limits of telescope portability, or have
lots of money, or like technology, go ahead and buy fancy accessories.
I won't tell, provided you remember that (A) aperture wins.

    In any case, I will mention some plain-vanilla accessories that you
might want to have, and maybe a few chocolate ones, too:

 (a) Eyepieces. A small number of good ones is better than a large
number of bad ones. You will need a low-power, wide-field eyepiece,
both for finding things and for low-power views of big, diffuse objects.
It might give a magnification equal to five or six times the telescope
clear aperture, in inches.  On my f/11 Celestron 14, the low-power
eyepiece has a 55 mm focal length, and is mounted in a two-inch barrel,
so that the front lens -- which sets the field diameter -- can be as
large as possible. (In little f/10 or f/11 telescopes, internal baffles
may mean that no light gets to the edges of a two-inch wide eyepiece; if
so, don't bother with the extra cost of one.) On my f/5 8-inch Dobson,
I use a 20 mm eyepiece, which doesn't need a two-inch barrel.

    The next power you will likely reach for is medium to medium high,
for a good look at detail in the object in view. Such an eyepiece might
give a magnification of 20 to 30 times the telescope clear aperture, in
inches. On my C-14 I use a 12.4 mm eyepiece, and on my 8-inch Dobson, a
4 mm. The objects you look at with high power probably won't be very
wide (though they might be), so for economy, you might not want a
super-wide-field type.

    Your next choices will depend on what you like to look at.  If you
are not sure, hold off buying more eyepieces till you find out.

    "Fast" f-numbers, typical in Dobson-mounted Newtonians, require
fancy, expensive eyepieces to give good views, because the steeply
converging light cones of these instruments are difficult for an
eyepiece to cope with, particularly away from the center of the field.
Slower instruments can use simpler eyepiece designs. It is a "Catch-22"
of amateur astronomy, that cheap telescopes (fast Dobsons) need
expensive eyepieces, but expensive telescopes (most refractors and
Schmidt-Cassegrains, with slow f numbers) can use cheap eyepieces.

    "Zoom" eyepieces, which change focal length at the twist of a
knurled ring, tend not to be very good. Barlow lenses, also called
telextenders, multiply the focal length of the telescope with which they
are used: It used to be that they generally worked well only with
telescopes with large f-numbers, where they were not needed -- another
"Catch-22". Yet I have heard that there are now Barlow lenses that work
with fast telescopes, where they are indeed needed, but I urge a
try-before-you-buy approach to selecting one.

    For over fifteen years I used an eyepiece set bought in roughly
1980. It featured no fancy designs, just a 55 mm Plossl, 32, 20, and
12.4 mm Erfles, and 7 and 4 mm Orthoscopics. The 55 and 32 mm eyepieces
were in 2-inch barrels, the others in 1.25 inch barrels. All were very
good quality -- the 55 and 32 mm were from University Optics, and the
others were Meade Research-Grade. All worked reasonably well even at
f/5, and the 68-degree apparent field of the Erfles was enough that I
was untempted to buy wider-field types. Besides, a big Erfle is already
so heavy that I must rebalance the telescope to use one. I did use the
4 mm eyepiece on the C-14 now and then, but occasions where I want that
much power are rare.

    In mid 1996 I bought more eyepieces, mostly out of curiosity.  I
found that decent Plossls are comparable to decent Orthoscopics. I
bought several Vixen "Lanthanum" eyepieces, which have built-in matched
Barlow lenses to give 20 mm eye relief, even at such short focal lengths
as 2.5 mm. I don't need glasses to observe, but even so, long eye
relief makes viewing more relaxed -- I'm not worrying about bumping the
eyepiece. It also facilitates public viewing -- I focus with my glasses
on, and tell everyone to leave theirs on and not refocus.

    Note what high-tech eyepieces can and cannot do. The best give
wider fields of view, with fewer eyepiece aberrations near the edges,
than older types. The improvement is most noticeable at fast f numbers.
If that's important to you, you might want some. But eyepieces are not
aperture stretchers. They can neither increase image detail beyond the
theoretical limit for the aperture, nor increase the number of photons
that make it to the focal plane. If you think otherwise, you are making
the same mistake as the clueless beginner who buys a drug-store
refractor because it says "Magnifies 400 Times!!" on the box. The best
an eyepiece can do is not make things worse. A simple eyepiece, with
good coatings and well-polished lenses, will show all the on-axis detail
a telescope has, and absorb almost no light. That's what counts most
for astronomical work.

    In 1980, I bought 6, 12 and 25 mm Ramsden eyepieces -- an old,
simple, design -- for about ten dollars each. I use them at star
parties without telling what they are. They have only four surfaces, so
simple coatings give good throughput, and there are few chances for bad
polish to scatter light and ruin contrast. The field of view is narrow,
but on axis, at slow f numbers -- f/10 or longer -- they give up nothing
to new designs; images are superb.

    (b) Finders. What kind of finder you get depends on how you use it.
If you plan on looking mostly at fine details in bright objects, then
you might buy a big finder, in the hope that most of what you look at in
the main telescope will be visible in it, too. But that won't work if
you push your telescope to its faint-object limits -- you would need a
finder as big as the main telescope. You might then consider a finder
that will show stars exactly as faint as on your charts. It helps a lot
in identifying what you are looking at through the finder, if every star
you see is charted, and vice-versa. Once the right pattern of stars is
in the finder, you can put the crosshair where the object lies, even if
it is too faint to see.

    In dark sky, the 10x40 finder on my C-14 shows stars to about
magnitude 9.5, which matches my big charts. The 7x35 on my 6-inch
Maksutov does almost as well. In suburbia, the 5x24 finder on my 8-inch
Dobson goes to about magnitude 6.5 (which would be the naked-eye limit
in darker conditions), thus matches many naked-eye star atlases.

    Unit-power finders, like the Telrad, let you to stare at the sky
with both eyes open and see a dot, circle or crosshair of light where
your telescope is pointing. A peep sight, made by taping bits of
cardboard to your telescope tube, may work as well, and will be much
cheaper, and any magnifying "straight-through" finder (in which you look
in the direction the finder is pointing) can be used with both eyes open
-- let your brain fuse the images, so you can use the finder's crosshair
with the other eye. I tried a unit-power finder (Orion's) on my 90 mm
refractor, but found it always inferior to the original 6x30 finder.
    My opinion about unit-power finders is in the minority. Many prefer
them to those which magnify. Some folks use the Telrad's circles of
known diameter to measure angular distances when finding things.

 (c) Charts. Preferences vary greatly. What I find useful, in order
from simple to complicated, is more or less the following:

 (c.1)    A simple planisphere, preferably a plastic one that won't
          sog out with dew and that may survive being sat upon. It's
          a fast way to find out whether a particular object is up
          before I go observing, or to determine how long I have to
          wait before it is well-placed.

 (c.2)    A "pocket atlas". I am particularly fond of Ridpath and
          Tirion's _The_Night_Sky_, from Running Press in Philadelphia,
          PA. It is about three by five inches and half an inch thick,
          and it is out of print. Write Running Press and complain.

 (c.3)    A "table atlas", bound as a book that will lie reasonably
          flat, showing stars to the naked-eye limit and lots of
          deep-sky objects to boot. I happen to use an old Norton's
          _Star_Atlas_; there are lots of others.

 (c.4)    A "deep atlas", such as _Uranometria_2000_ or the AAVSO
          atlas, with a stellar magnitude limit of 9 or 9.5 and a vast
          number of objects. What's important here is to have enough
          stars charted that there are plenty in every finder field.

 (c.5)    A planetarium computer program (Bill Arnett reminded me).
          If you are a beginning astronomer, I do *not* suggest you
          rush out and buy a computer, but if you already own one, you
          might bear in mind that there are programs that will turn
          your console into a window onto the simulated heavens, with
          features for finding, displaying, and identifying things.
          I happen to have the rather old Voyager 1.2 for my even
          older Macintosh II; there are plenty more, both for Macs
          and for the world of MS-DOS and its descendents.

          Some folks run such a program on a laptop, at the
          telescope. Please put red cellophane over your console,
          if you do.

 I have had limited use for the popular oversize-format charts with
lesser magnitude limits, like 7.5 to 8.5; they don't show enough stars
to be useful with most of my finders, and are too cumbersome. The
plastic-laminated versions make good place mats, though. Everyone
should use the box of a Dobson as a picnic table at least once.

 (d) A red flashlight, so you can read your charts and notes without
ruining your night vision, or that of people near you. The kinds that
have a red light-emitting diode (LED) instead of a flashlight bulb are
particularly good. If other observers scream and throw things, your
light is probably too bright.

 (e) A logbook. This item is not for everyone, but I find it useful
to record my observations, even if I don't do anything other than note
that I saw a certain object with a certain telescope and magnification.
Logbooks make fun reading when it is cold or cloudy, and often there
will be reason to look up something long after the fact. Besides, if
you quote frequently from your logbook, you can make your friends think
you are an active observer when you really gave it up years ago.

What about observing skills?
===========================

 Even some experienced amateur astronomers think that seeing things
comes free and easy, with no more effort than opening your eyes: But as
currently popular slang so evocatively articulates,

                             ** NOT **.

Vision is an acquired skill. You must learn it, you must practice, and
you must keep learning new things, and practicing them, too.
Buying a bigger telescope to see more is like buying a bigger kettle
to be a better cook, or buying a bigger computer to be a better
programmer. Not that it won't help -- it might -- but cooking and
programming depend far more on knowledge and experience than on
artifacts. So does visual astronomy. People with garages full of
telescopes (pardon me while I try to close the door to mine) are in
great part victims of materialism, marketeering, and hyperbole.
Practice is cheaper, and works better. As I said near the beginning of
this article, an experienced observer may see things with a small
telescope that a beginner will miss with an instrument five times
larger, even with objects and sky conditions that favor both equally.

  What skills may you hope to cultivate? What techniques should you
practice? Not all have names, but here are a few, in what I think is
order of importance; what matters most comes first.

 (a) Patience. It can take a long time to see everything in a field,
even if you know exactly what you are looking for.

 (b) Persistence. Eyes, telescope, and sky vary from night to night.

 (c) Dark adaptation. Avoid bright lights before observing: It takes
your eyes hours to reach their full power of seeing faint objects.

 (d) Averted vision. The part of your retina that sees detail best,
sees low light worst. Look "off to the side" to find lumps in the dark.
    Many observers use averted vision on faint objects, but not for
faint detail in bright ones. Detecting something doesn't mean you've
seen all you can. Don't let the dazzle of a galaxy's lens keep you from
tracing spiral arms out beyond the width of the field. How about
increasing magnification, and using averted vision to see if you can see
more detail in the paler, but larger, image?
    Averted vision helps with double stars, when one star is much
fainter than the other, even if the faint star is bright enough not to
need averted vision if it were by itself. That is, averted vision seems
to facilitate the detection of low contrasts as well as faint objects.

 (e) Stray light avoidance. Even when it's dark, background glow
interferes with detecting faint objects. Keep it out of your telescope
and out of your eyes. Try eye patches and eye cups for eyepieces.
My first view of the Sculptor Dwarf Galaxy was with my jacket collar
pulled up over my binocular eyepieces. I looked like a cross between
the Headless Horseman and the Guns of Navaronne, but I saw the galaxy.

 (f) Moving the telescope. The eye sometimes detects motion, or
changing levels of brightness, more easily than static images. Jiggle
the telescope, or move it back and forth, to make an object "pop out".
Try it while using averted vision.

 (g) Not moving the telescope. The eye sometimes adds up photons
over many seconds; if you can hold your eye still for a long time,
faint things may appear. Try it with averted vision.

 (h) Respiratory and circulatory health. If you smoke, try taking a
break before and during observing -- carbon monoxide from incomplete
combustion interferes with the ability of the blood to transport oxygen.

    Clear sky, and enjoy your telescope.

                                                -- Jay Freeman
                                                   freeman@netcom.com

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.
(Note: Dobsonian Telescopes are mounted this way)

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.

Binocular Telescope
 A set of Dobsonian telescopes mounted so their eyepices form
a Binocular 3D view of the sky.

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 magazine:
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,
different 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 crystals
(notably fluorite) are sometimes used to compensate for the
aberration. Such telescopes are termed "achromat," or "apochromat"
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).

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.
Note: That this design is now the #1 Design seen at many Star partys.

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 magnifications) 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 measure 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 compromise); 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
generally  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 telescope
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 telescope
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 zenith).
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 equatorial
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 problem
for visual astronomy, but a limitation on astrophotography.

light bucket
 A common slang term for a large aperture. The cure for "Aperture
Fever."

Maksutov-Cassegrain
     See catadioptric.

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

Newtonian
     See reflector.

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.

reflector
 A reflector is any telescope which uses a mirror as its objective.
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 .

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.

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.

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.

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 telescopes
come with drives which compensate for the mechanical defects.

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
technical, 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.

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.

Nightwatch by Terence Dickinson is a good introductory book on
Astronomy. 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
quality.

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 telescope 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?

This is a very unfair question at the best. There are many companys
which make good telescopes. A lot will depend on just how much you
want to spend for a telescope. The Major companys that make and/or
sell telescopes are as follows: Orion Telescopes, Meade, and
Celestron, but you have to be carefull with what you buy from even
these companys,as they ALL are selling telescopes which are coming
from Prison factorys in 'RED CHINA' and are the same as the Junk
department store telescopes. There are other smaller companys that
make good scopes too. There are some Japanese companys that are
selling some very good telescopes and also some poor ones too.

Televue has a very good reputation, at a somewhat higher price.

Tasco is sold at Toys R Us, K-Mart, & Wal-Mart,etc. Waste of Money.
>>> Notice: Tasco has taken over Celestron, they are now one company,
    only time will tell if this inproves Tasco or Degrades Celestron.

Simmons: Total waste of money, worst than Tasco.

Bushnell: I have looked at this companys telescopes 1st hand and
I do not belive that they would withstand one full night of
useage viewing the sky. They are even WORST than Simmons! They
are so bad they make Tasco junk look good!

There are now a lot of smaller companys poping up that are selling
the same 'Made in Red China' telescopes uder names never seen before
it would be a good idea to stay away from them too.

There are some companys importing telescopes from Russia, I have not
seen these scopes first hand, but have read some good reports of
them.

6.2.  What Is The Best Telescope To Buy?

Once more this will depend on the answers of questions you need to
ask yourself. Are you going to use the telescope for just viewing?
or are you going to into the field of Astrophotography? Also it will
depend on how much you want to spend too. In the end,only YOU can
answer this question.

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.

As the numbers of companys who now either make and/or just sell
Telescopes of ALL price ranges, the list is just to much to put
into this FAQ, instead, the next section will list a number of
both large and small companys that market telescopes. The best
idea would be to contact the comapnys and find out what kind of
telescope they market in your price range. Then if you can,
Find one of those telescopes at a Star party.

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 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 significantly
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 (limited) lifetime
warranties on their optics, which are not transferable.

All that having been said, here is a list of places you can buy
telescopes, with comments as applicable. Note that not all will sell
or will ship. To you, some you must go to a store.

Orion Telescopes
P.O. Box 1158\par
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. If you need technical
assistance when you call, ask for Steve or Eric. They have a very
good service and support record.

Lumicon
2111 Research Dr. #5
Livermore,Ca.94550

While I have not had any dealings with this company,the messages
I've seen on sci.astro.am have all had good things to say about them.

Astronomics
2401 Tee Circle Suites 105/106
Norman, OK 73069

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.

Celestron International/TASCO.
2835 Columbia St.
Torrance,Ca.90503

This company also sells many types of telescopes. From SCT's to
DOBs. Have seen both Good and Bad posted about them. As Noted above
this company is now owned by TASCO.

Mag 1 Instruments
16342 Coachlight Dr.
new Berlin,Wi.53151

Markets their 'Portaball' style DOBs in 8in and 12.5in size.

Mead Instruments Corps.
6001 Oak Canyon
Irvine,Ca.92620

Markets many types of Telescopes, from junk to High End.

Coulter Optical
Div. of Murnaghan Instruments
1781 Primrose Ln.
West Palm Beach,Fl.33414

They market a full line of DOBs.

Obsession Telescopes
P.O.Box 804a
Lake Mills,Wi.53551

Markets Dob's from 15in to 30in!

Pocono Mountain Optics
104 N.Plaza
Moscow,Pa.18444

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 dissatisfied.

Roger Tuthill
11 Tanglewood Lane
Dept. ST
Mountainside,N.J. 07092

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

Stargazer Steve
1752 Rutherglen Cr.
Sudbury, Ontario
P3A 2K3 Canada

Markets a 4 1/4inch DOB in both Kit form and/or ready-to-use.
Both under $300.00.
Also a 6inch DOB kit for under $450.00 with shipping.

Starsplitter Telescopes
3228 Rikkard Dr.
Thousand Oaks,Ca.91362

Markets DOBs from 8in to 30in.

University Optics
P.O.Box 1205
Ann Arbor,Mi.48106

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

Parks Optical
270 Easy St.
Simi Vally,Ca.93065

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 telescopes 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 lot of bad reports, order at your own risk!

Also there is the AstroMall.

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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
telescope: 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 project 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
telescopes 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.

The video (also excerpted from the order form): For the first time
on video, John Dobson shows how you can build your own low-cost
Dobsonian Telescope. The 90-minute video is a complete step-by-step
guide, covering telescopes from 8 inches to 16 inches in diameter.
$39.95 +$3.50 shipping.

7.3 What is the Best Mount?

            EQUATORIALS Vs. ALTAZIMUTHS: THE TRUTH

   The various telescope mounting systems available for use
by amateur astronomers have been discussed at length on
sci.astro.amateur. There has been a great deal of debate,
a little ill-informed opinion, and some real misconceptions
concerning each of the basic mounting schemes, so perhaps it
is time to clear the air. One basic and irrefutable fact must
be stated up front: NO MOUNT SYSTEM IS PERFECT FOR ALL SITUATIONS!
Any attempt to champion one mount scheme over another without
considering all the facts is doomed to failure. Below are the
true advantages and difficulties of the two most popular
mounting sytstem.

The ALTAZIMUTH (ie: Dobsonian, ect.). This mounting system
has gained considerable popularity over the past 20 years,
evolving from the old "pillar and claw" system originally used
only in inexpensive small telescopes, to a modern well-designed