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

There are a lot of people who are anxious 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.

Basic Rules Before You Buy

Glossary of Common Words (New!)

The Find-A-Scope Store. Recommended books, scopes and accessories from Amazon. (new)

Recommended Books, Videos and Software

What Scopes To Buy (and what not to buy)

Department Store Scopes
Cheap Scopes
Very Cheap Scopes
Medium priced scopes
4.5" Reflectors
Portable Scopes
Short Scopes
Those cheap 6" Refractors
Astrophotography
Deep Sky scopes
Expensive Scopes
I gotta have a computerized scope!
"Price is no limit" Scopes
Questars
Used Telescopes
Scopes to Avoid

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?
Can I use a camera lens as a telescope?
How can I test a telescope?
I bought an inexpensive Bushnell/Tasco/other scope at a yard sale...
A note on optical quality

Both guestbooks are now closed as I don't have time to filter out spammers anymore.

Let's start with some basic rules:

Never buy a telescope in a department store. I used to qualify this rule, but I've decided to make it absolute. Similarly, don't buy telescopes from "close-out" catalogs, stores that specialize in high-tech toys, catalog showrooms, etc. Don't buy from anyplace that doesn't do a major business in astronomy related tools.

"Christmas Trash" telescopes. Every fall, thousands of cheap, useless telescopes flood the toy stores and department stores. These instruments look like telescopes, and are offered at what look like bargain prices. And they're junk. These are what we call "Christmas Trash" telescopes. They havebadly figured lenses- some of them plastic- cheap, wobbly mountings, unusuable eyepieces, and outrageous claims of 400x and 640x, and sometimes 1200x magnification. Often they're sold in respectable department and discount stores. Stay away from these. They are a waste of money, and will do nothing but destroy a child's interest in astronomy.

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... 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.

I just picked up a 40mm Unitron refractor made in the 1960s- that's a 1.6" telescope! But it has a very long forcal length (700mm- that's f/17.5), very high contrast, and a really solid mount. It can split double stars and provide planetary views that would be impossible in a lot of cheap department store scopes. It sold for $75 back in the 1960s; that's close to $500 in 2007 dollars.

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 4" TeleVue Genesis 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 focusing impossible. That's why those simple-looking Dobsonian reflectors are so good. They're as stable a a rock. Even my little 2.7" Pronto is mounted on a TeleVue Upswing head 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 2.7" scope. Now you don't have to spend that much, but it points out why a $120 refractor with included tripod and head isn't going to be terribly stable.

Before You Buy...

A telescope is a useful tool- but only if you know what to do with it. Before you decide to get a telescope, you should spend a little time reading about telescopes to get a better idea of what they can do, and to better understand your own needs. If at all possible, find an astronomy society or club you can visit to get some personal experience using different telescopes. Too many people spend a lot of money on a scope with unrealistic expectations of what they'll be able to see. Others get discouraged when they find they can't just point the scope heavenwards and see amazing sights.

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 well 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 Edelmanmje@spamcop.net

While I'm glad to help where I can, please read all the pages 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 in 1997, 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.

Links to other interesting sites:

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/. You can find a lot of articles and reviews at http://cloudynights.com as well as some interesting projects.

If you have any intentions of doing astrophotography, you need to look at Michael Covington's web site, and preferably his book, too. He'll answer all your questions and show you how to do it right.

For some very good viewing tips for beginners, See Emil Neata'sNight Sky Info - Weekly information about the night sky, astronomy articles and observations.

Fritz Kleinhans, Resident Astronomer Emeritus at Indiana University-Purdue University Indiana, has a web page for a Backyard Astronomy class he teaches with some good reference material for beginning astronomers and those running their own classes. The Project List offers a number of ideas for projects of interest to amateur astronomers.

` When it's too cold, rainy, or bright out to observe, you can entertain yourself by reading my blog about food and cooking. (It's really quite interesting.)

There are a lot of good astronomy sites on the web, but beware- there are a lot of site that are merely collections of ads, or material scraped from other web pages designed as a vehicle for advertising. I periodically get solicitations from these sites asking for a listing on my page in return for a listing on theirs. Read as much as you can, but learn to distinguish the writing of experienced amateurs from people merely trying to take your money.

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