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From: eugene@ames.UUCP (Eugene Miya)
Newsgroups: net.astro
Subject: Small projects for net.astro
Message-ID: <798@ames.UUCP>
Date: Wed, 13-Feb-85 20:16:47 EST
Article-I.D.: ames.798
Posted: Wed Feb 13 20:16:47 1985
Date-Received: Mon, 18-Feb-85 05:33:34 EST
Distribution: net
Organization: NASA-Ames Research Center, Mtn. View, CA
Lines: 85

In the past few weeks, I've seen two very similar postings: how-do-you-
buy-a-telescope and who-has-machine-readable star catalogs.  These same
questions have appeared before.  I would like to propose [with my one
good hand] that we on the net make a few short documents in the net.news
spirit answering frequently asked questions.  Long term members of the
net can keep copies and either repost or mail these questions as new members
ask.

In this spirit, let me say that we have the STARMAP system from NASA GSFC
as well as the Yale bright star catalog.  We have made a small number of
copies, but as I recently injured myself in such a way that making tapes
is difficult, perhaps others can help out here.  Note: most of these catalogs
contain volumes of information which many amateurs would have no need:
some software company can market a condensed star map for micros/amateur
systems.....

In the spirit of purchasing, selecting, making scopes telescopes,
let me present an outline which people can add their comments and
throw tomatos:

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

		ADVICE FOR TELESCOPE PURCHASERS

			E. N. Miya
			and others on the net
			[add your name and we'll integrate it
			it somehow, don't worry]

SO YOU WANT TO BUY A TELESCOPE
Avoid impulsive buys.  Don't, unless you really have to [e.g., astro
photography, is an exciting, but non-trivial hobby.]
If you just want to look at stars,
planets, nebula, or Halley's Comet, looking through a local planetarium's
or community college's [university's] telescope will probably be far better,
and you won't have something collecting dust after a while.

Realize that the Andromedia Nebula (M31) will never appear to the naked eye
as it appears in photographs taken over hours of exposure.
TRY DIFFERENT TELESCOPES
There are companies which rent telescopes (in large cities) or can
provide demos for universities.  Ask around your area.  Join amateur
associations.
TYPES OF TELESCOPES
	REFRACTORS
	REFLECTORS (aka Newtonian)
	COMPOUND SYSTEMS
Questars and Celestrons fall into these areas.
SELECTING AN OPTICAL SYSTEM
You need to ask yourself, what are your reasons for purchasing the telescope.
For purposes of net.astro, we will assume astronomy.
The first (and less important) thing first time telescope buyers consider
is magnification "power."  Without detailing all the reasons, the single
most important factor in purchasing a good telescope is light gathering
power.  Get a telescope with as wide an aperature as possible.

Check for defects: bubbles in refractor optics on cheap telescopes are
not uncommon.

Another set of important considerations are the mount-types and clock drive.
It's difficult to see any image without a stable viewing platform.  Fixed,
sheltered piers are best.  Tripods are systems of last resort.

Eye pieces are an important set of accessories.
TESTING AN OPTICAL SYSTEM
You can make some simple optical tests to be viewed at a distance to
see problems such as spherical and chromatic aberrations.
LEARN HOW TO LOOK THRU AN ASTRONOMICAL TELESCOPE
[discussion on cones and rods in the eye and peripheral viewing.]
LONG TERM TELESCOPE CARE
Reflector systems should be occasionally re-silvered.
REFERENCES
For instance [I have few astro books in my office (they are at home)]:

%T Amateur Telescope Making, Vol. I, II, III

---------------------------------------------------------------------
my right arm is getting tired.  we can refine this without
duplicating some basic text. in particular, a good set of references
would help novices considering such a purchase. so long till July.

--eugene miya
  NASA Ames Research Center
  {hplabs,ihnp4,dual,hao,vortex}!ames!aurora!eugene
  emiya@ames-vmsb.ARPA