Guide to Buying a Telescope
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 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.. Talk to the people first
and ask for advice if required.
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.
So apeture with quality glass is whats required, watch out because some cheap scopes have plastic lens.
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 9x63 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.
That's why those simple-looking Dobsonian reflectors are so good.
They're as stable a a rock. Most good
telescopes have metal mounts, avoid plastic rubbish.
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. It takes some work, check
these links for help:
1.
Types of Telescopes 2.
Telescope Help
Know what to expect
The views through your telescope simply will NOT match what you see in astrophotos in magazines or even on the box of your scope. Period! First, you will not see nebulae in color, planets will look tinier then you expect and will lack most of the color and contrast you see in books and magazines. Most people that look through a telescope for the first time are somewhat disappointed about what they see, or what they don't see. Don't get me wrong, you will never forget the first time you see Saturn or the Moon in a telescope and the "Wow!" that escapes your lips will amaze you also, but the "faint fuzzy" stuff often disappoints first time viewers.
Still baffled, then contact us for free advice, or listen to this Podcast from
www.astronomycast.com a guide to buying equipment brought to us
by Pamela and Fraser.Check out these links to get an idea of what you can see in different size telescopes, a very useful website:
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