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Purchasing Amateur Telescopes FAQ

Ronnie B. Kon
ron...@cisco.com

Last Updated: September 12, 1994

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

Questions in this FAQ:

1. What is the single most important thing I should know before
buying a telescope?
2. What is the single best piece of advice to give to someone
thinking about buying a first telescope?
3. What Does All the Jargon Mean?
4. What Are Some Good Introductions To Amateur Astronomy?
5. What Will I Be Able To See?
6. Buying A Telescope
6.1 What Company Makes the Best Telescopes?
6.2 How do Meade and Celestron Name Their Telescopes?
6.3 Comparison of Schmidt-Cassegrains
6.4 What is the Best Telescope to Buy?
7. Where Do I Buy My Telescope?
7.1 What About Buying Used?
7.2 What About Building A Telescope?
8. What Accessories Will I Need?
9. What are Digital Setting Circles?
10. Why Should I Start With Binoculars?
10.1 How Do I Hold Binoculars
11. What Books and Star Charts Are Recommended?
11.1 What About Computer Programs?
11.1.1 What Programs Can I Get For Free?

Contributors to this posting include:

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

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

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

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

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

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

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

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

3. What Does All the Jargon Mean?

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

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

aperture
The diameter of the objective.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

f/10, f/6.3
See Focal Ratio

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

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

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

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

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

In general, the slower the telescope the more forgiving it is of
optical errors in the objective and eyepiece. A telescope of
f/10 is fairly forgiving, f/6.3 much less so.

focuser
This is the thing that holds the eyepiece. It moves in and out
so you can focus the telescope. It is always included with the
telescope when you buy one. The size, almost always .965", 1.25"
or 2" refers to the barrel diameter of the eyepieces it accepts.

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

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

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

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

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

Maksutov-Cassegrain
See catadioptric.

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

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

Newtonian
See reflector.

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

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

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

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

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

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

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

right ascension
See declination.

Schmidt-Cassegrain
See catadioptric.

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

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

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

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

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

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

4. What Are Some Good Introductions To Amateur Astronomy?

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

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

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

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

P. Clay Sherrod's A Complete Guide to Amateur Astronomy, available
through Sky Publishing Company, is a more technical introduction.

Sidgewick's books are absolutely excellent books, probably the very
best ever written on amateur astronomy. They are also probably over a
beginner's head. Holding off on these for a while would not be a bad
idea.

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

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

Also see below, the section on Books and Starcharts.

5. What Will I Be Able To See?

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

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

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

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

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

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

6. Buying A Telescope

6.1. What Company Makes the Best Telescopes?

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

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

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

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

6.2. How do Meade and Celestron Name Their Telescopes?

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

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

Meade has recently introduced the LX100 and LX200 series of tele-
scopes. The LX refers to the drive (Meade has a very strange habit of
changing what LX means--it used to refer to the drive, then
(apparently) the focal ratio, now it's back to being the drive), which
are certainly the most wiz-bang on the market. The LX200 has a
computer 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.

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.
Useless 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, a 2x barlow, and a moon filter (and
some other junk I don't think should figure into your purchace
decision, so I'm not going to mention them).

I don't know if I'd recommend the 60mm version of the above,
which sells for $344, as it strikes me as simply the TeleVista (a
telescope I've heard bad things about) on an equatorial mount.
If you can afford the extra $200 on the mount, spring another
$200 to get the 80mm objective (which gets 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
physical and optical axes: the view was sharper from one rota-
tion 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.

7. OK, Where Do I Buy My Telescope?

Well, there are three basic places:

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

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

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

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

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

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

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

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

Orion Telescopes
2450 17th Avenue
Santa Cruz, CA 95061
(and two other locations)
800-447-1001
800-443-1001 in California

Orion Telescopes carries a wide selection of binoculars, telescopes,
and accessories. They also have a 30 day "no questions, satisfaction
guaranteed" refund policy. The people who work there strike me as
knowing very little about telescopes. In particular, they are almost
entirely ignorant about Meade products, and seem largely indifferent
about selling them. However, a number of people swear I am dead
wrong: that the salespeople are very knowledgeable. I can only con-
clude that I've been getting all the wrong salespeople. In any case,
their products work, and they do seem serious about their guarantee,
which is one of the best I have ever seen. A fair number of people
(me included) have said that they have bought at Orion and all are
very satisfied with the way they were treated. This place is fairly
expensive, and they have the sleazy policy of charging a "stocking
fee" if you buy from the store, which always seems to be the same as
the postage and handling fee for mail ordering from their catalogue.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Refer to Adorama. Same comments apply.

Pauli's Wholesale Optical
Danbury, CT

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

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

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

7.2. What About Building A Telescope?

This section was written by Andy Michael.

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

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

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

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, cov-
ering telescopes from 8 inches to 16 inches in diameter. $39.95 +
$3.50 shipping, same address.

8. What Accessories Will I Need?

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

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

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

9. What Are Digital Setting Circles

This section was written by Jim Van Nuland

9.1. What Are They?

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

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

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

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

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

9.2. Must the ground board be leveled?

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

9.3. How does one set up an equatorial mounting?

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

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

9.4. Do the DSCs support a Poncet platform?

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

9.5. How accurate is the device?

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

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

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

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

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

9.6. What objects are in the internal catalog?

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

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

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

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

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

9.8. What is "identify" mode?

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

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

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

9.9. Can it replace star charts?

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

9.10. What other functions are present?

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

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

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

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

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

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

9.12. How accurately SHOULD the mount be constructed?

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

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

9.13. How accurately should encoders be installed?

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

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

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

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

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

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

9.14. How accurately MUST the mount be constructed?

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

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

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

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

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

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

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

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

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

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

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

10. Why Should I Start With Binoculars?

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

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

The remainder of this section was written by Paul Zander.

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

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

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

You might also use a plastic pad to lie on.

10.1. How Do I Hold Binoculars?

This section was written by Jay Freeman.

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

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

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

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

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

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

10.2. What Are Some Eye Relief Figures?

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

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

11. What Books and Star Charts Are Recommended?

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

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

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

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

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

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

All the materials listed are available from:

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

Their catalog is free.

11.1. What About Computer Programs?

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

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

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

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

The latter is available from

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

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

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

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

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

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

It also has a fairly comprehensive deep-sky database.

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

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

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

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

11.1.1. What Programs Can I Get For Free?

Well, I use a program called ephem, for calculating a whole lot of
stuff (like ephemerides, phase (of moon and planets), dawn, dusk, etc.
and like it a lot. There is a motif based upgrade, xephem, which I
have not used yet. You can pick it up from export.lcs.mit.edu in
contrib/xephem/xephem_2.1.tar.Z. Ephem and xephem were written by
Elwood Downey.

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

For Macintoshen there is a free/shareware program MacAstro available
from cs.dal.ca in /pub/comp.archives/macastro and from
aix370.rrz.uni-koeln.de in
/.disk2/usenet/comp.archives/sci/astro/macastro. It will show the sky
at any time, including stars, sun, moon and planets. It will also
give the rising/setting times of the sun and the moon. It is
shareware, $20, written by Nicolas Mercouroff (n...@cs.brandeis.edu).
--
-------------------------------------------------------------------------------
Ronnie B. Kon | "You couldn't deny that, even if you used both
hands"
ron...@cisco.com |
(415) 688-4592 | -- The Red Queen

-------------------------------------------------------------------------------

[Icu]

Uit de I(uchieven:

4. I found an injured bird; what can I do?

Most people's encounters with injured wild birds happen around plate-
glass windows. Birds strike glass windows and doors frequently,
apparently
because of the reflections of sky they create. In most cases, the bird
is simply stunned. The best way to save the bird's life is to shoo
potential predators from it until it recovers and flies off.

If you find a large bird, such as an owl, a hawk, or a vulture, that
has been wounded, you may wish to contact a rehabilitation center, such
as the Carolina Raptor Center (+1 704 875 6521) or the Vermont Raptor
Center (+1 802 457 2779), for assistance.

Be aware that touching large wild birds can be dangerous.

[de Yeti]

In article <3318cb1c...@news1.xs4all.nl>, icul...@domain.nl (Icu)
wrote:

> Uit de I(uchieven:
>
> 4. I found an injured bird; what can I do?
>

> []

>
> Be aware that touching large wild birds can be dangerous.

Snif, heel ontroerend! Dank je wel I(u, snif, dat was heel mooi.

de Yeti, snif