The Heretic's Guide  to Choosing and  Buying Your First Telescope

There are a lot of people who are dying to own a telescope to view the heavens above, but who need
direction as to what scope to buy. This is my FAQ, and while I try to be objective, it does reflect my viewing
biases. For some contrasting views from someone whose opinion I value, see Jay Reynolds Freeman's intro
on his page at Todd Gross' site.  Ed Ting has an excellent (and huge!) collection of reviews of specific scopes at
http://www.scopereviews.com/ .

Basic Rules Before You Buy

Recommended Books, Videos and Software

What Scope To Buy

Frequently Asked Questions:

Where should I buy my scope?
What are f/ratios?
What's better, a reflector or a refractor?
What's a good scope for a child?
Are those little refractors really better than a bigger scope?
What eyepieces do I need?
A note on optical quality

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Let's start with some basic rules:

          Magnification by itself is meaningless. Don't choose a telescope by its advertised magnification.
          The way to compare similar telescope is by aperture; that is, the size of the objective lens or
          mirror. As a rule of thumb, few scopes can deliver more than 50x per inch of aperture under the
          best conditions; That means that the 2.5" (60mm) telescope advertised as a "625x telescope!"
          is really a 125x scope at best! A lot of the really interesting objects out there are very large,
          but very dim. The Great Galaxy in Andromeda - one of the most majestic sights in the sky- is
          eight times the size of the full moon, but a lot dimmer. A magnification of 20-40x is all you'd
          ever want to view it. This leads to...

          There's no substitute for aperture. All things being equal, size counts. Larger is better. But
          there's a caution that goes with this:

          There's no substitute for optical quality. A small scope with excellent optics can see more than
          a large scope with mediocre optics. I stood in line at a star party a while ago to look at M31,
          the Great Galaxy in Andromeda, through a 21" telescope. I imagined I'd see dust lanes,
          structure, maybe even individual stars...what I saw was a fuzzy blob of cotton, with less
          structure than I'd seen in my 3.5" Questar! The owner was as proud as can be of this white
          elephant. He'd never looked though a good scope. See the FAQ for some comments on why a
          high-quality small  scope can be a far better choice than a large scope.

          There's no substitute for darkness. What does this mean? It means if you have to choose
          between a huge scope that sits in your light polluted city back yard, and a small scope that
          you can carry out to remote, dark areas, go small and transportable. I can see more with my
          2.7" scope under a really dark country sky than I could with my 10" scope in my suburban
          back yard.

          The smaller the scope, the more often it gets used. My 8x56 binoculars get used just about
          every clear night. The 2.7" Pronto comes out a lot too; it only takes a minute to set up. The
          Questar comes out a number of times every week in warm weather, and occasionally in cold
          weather. The 10" Newtonian that I spent 6 months restoring and improving spent most of its
          life in my garage. Loading it into the car- a five-foot long tube, and a huge mount made of steel
          and cast iron that weighed well over 100 pounds- was a major undertaking.

          The mount is as important as the scope. Without a solid, steady mounting, you can't even
          focus properly, let alone view or do things like photography. Those scientific looking mounts
          on cheap telescopes may look good, but they're absolutely worthless. They shake like crazy
          and make focussing impossible. That's why those simple-looking Dobsonian reflectors are so good.
          They're as stable a a rock. My current mount for the Genesis and Pronto is a TeleVue Upswing head
          mounted on a Gitzo 320 tripod- that's a pretty heavy-duty photographic tripod that costs $300 by itself!
          Add the Upswing and you're talking $460 for a simple alt-az mount to support a 3" or 4" scope. Now
          you don't have to spend that much, but it points out why a $120 refractor with included mount isn't
          going to be terribly stable.

Before You Buy...

If you're already set on observing the moon and the planets, then by all means, go ahead and buy a telescope. If you are more interested in deep sky objects like galaxies and nebulas, you would do wel to spend time learning the sky with the aid of a simple star atlas and a pair of binoculars.

If you have specific questions about something I've written, feel free to e-mail me. I'll try to help if I can. If I don't know I'll try to refer you to someone who does. If you have suggestions for improving this page I'd like to hear from you, too.

Michael Edelman mje@spamcop.net

While I'm glad to help where I can, please read the page before asking for help. I probably receive two or three e-mails a week asking a question that's answered above. Most of them are asking for my opinion on a cheap 4.5" scope (no) a department store scope (no) or a cheap import sold under the Bushnell, Tasco or Jason label (no).

Some of you have asked: Why "Heretic's" guide? Well, it's because when I wrote the first version some years ago, it was contrary to most of the other FAQs out on the web. The typical advice given was to buy a Celestron or Meade 8" SCT, as if that was the only choice for "serious" amateurs.  Since that time, more amateur astronomers have discovered the advantages of smaller scopes, the higher contrast available in good refractors and the advantage of Maksutovs, and the market has responded in kind. Now, of course, you hear different sorts of nonsense, and some companies are marketing junk refractors and Maksutovs!

There are still some points of view held to here that you'll see disputed elsewhere. Often you'll read "there's no substitute for aperture" with the necessary qualifications about quality, or that "you need a long focal length for high magnification" or "you need a short focal length for wide angle views".  Thus I suppose I still hold some heretical views- but mine are backed up by observation and physics.