Remember, however, that the main function of a telescope is to gather light. Making things a lot bigger is often not as important as you might think. Many beginners mistakenly place too much emphasis on a telescope’s magnification. Toy store telescopes try to attract the unwary beginner by claiming unusably-high magnifications, like powers of 675x from a scope that can realistically reach only 125x or so.

Don’t be taken in by those exaggerated claims. It’s a rare telescope, and generally a large and expensive one, that can give satisfactory views at 675x, no matter what it says on the pretty box the toy telescope comes in. Think of it this way. If you’re looking at something small in a dark room, what you need most to see it is more light, not a magnifying glass. This issue is covered more fully in our FAQs “How Much Power Do I Need?” and “How Big a Scope Do I Need?”

Many of the objects at the top of a beginner’s observing list are quite large. The Andromeda Galaxy is actually over 3° across – more than six times the diameter of the Moon. You don’t need a lot of power to see something that big! Except for its small and bright core, however, it’s too faint to see with your unaided eye. You need a lot of light-gathering to see Andromeda, not a lot of magnification.

Magnification is important when you want to get up close and personal with small, bright objects – like details on the Moon and planets. But keep in mind that there are many more faint deep space objects to see than there are bright planets. Unless your major interest is the planets, you’re more likely to be out looking at big faint nebulas rather than small bright planets. While magnification is important for observing certain objects, light-gathering is still the most important telescope characteristic.

Resist the temptation to push the power too high in the beginning. Wait until you’re used to the scope’s performance and have a better feel for what you want to see. While a high power eyepiece makes objects look larger, it also magnifies the things you don’t want to see – like shakiness in the telescope’s mount, or the blurring caused by atmospheric turbulence. The trick is to use the proper amount of power for the kind of object you’re looking at, at the time you’re actually doing the looking. These issues are covered more fully in our FAQ “How Much Power Do I Need?”

All of the performance measurements of a telescope (limiting magnitude, resolving power, maximum useful magnification, etc.) are directly related to a telescope’s aperture (the diameter of the light-gathering mirror or lens). The bigger the aperture, the better these performance measurements become. So, all other things being equal, you should buy a scope with the biggest main mirror or lens that is practical for you.

For many beginners, this means a telescope with an aperture 3 to 6 inches across, but this is not a hard and fast rule. Your budget may say “no” to that big a scope, or you may not have the room to store a big telescope. And remember, a big scope can be a chore to drag outside and set up every night. You could lose interest if setting up for observing becomes too much of a hassle.

What kind of a telescope mount do you need? Broadly speaking, telescopes sit on either an altazimuth mount or an equatorial mount. An altazimuth mount moves in altitude (up and down) or azimuth (right and left). To keep objects centered in the eyepiece as the sky rotates overhead, you move the scope in both axes simultaneously, generally by either turning manual slow motion control knobs (on smaller scopes) or by pushing the telescope tube by hand (on large Dobsonian reflectors).

An equatorial mount also has two axes, but the scope is tipped over so that one of the axes points at the north celestial pole. This allows the scope to follow objects across the sky by turning on just one axis, the same way the Earth is rotating on just one axis around the north celestial pole. On manually operated telescopes, this means that you’ll have only one knob to turn (compared with the two needed to control an altazimuth mount scope). However, this type of mount often comes with, or has available as an option, a motor drive that will automatically move the telescope at the same speed as the stars (the sidereal rate). This keeps heavenly objects centered in the eyepiece without any work on your part. It also allows several people to observe without having to worry about losing the object when they change places at the eyepiece.

There are also computerized go-to mounts (often altazimuth types with motor drives) that will automatically move the telescope to any object you want to observe, and then follow it for as long as you want to look, without any work on your part other than pressing a few buttons on a hand control. There are a surprising number of these computerized go-to mounts available at prices well under $500.

Regardless of the type, a telescope mount should be sturdy and well built. The best optics in the world won’t perform very well if they are sitting on a wobbly mount that shakes every time you touch it. The mount should be at least as heavy as the telescope tube, preferably heavier.

Now that you have a general idea of what a telescope can do and how it does it, let’s start to actually choose the right telescope for you . . .