Buying A Telescope Anyone?

At the very start, by far the best thing to do is to find someone who knows a bit about it, and talk to them. If they own a telescope, flatter their vanity and ask if you can visit them one night to look at the sky together. They will be only too glad to share their enthusiasm and knowledge with you. A few hours spent with someone who has already been through the beginner's pitfalls will be invaluable. If you don't know anyone to help you out, give the Bendigo and District Astronomical Society a call. The Society meets monthly and is always happy to assist people in any way they can.

Secondly, don't be embarrassed by your ignorance. Everyone knows nothing when they begin, and there are (almost!) no such things as silly questions. There are limits to everyone's knowledge, and one of the best aspects of stargazing is that there is always something new and interesting to learn, even for the experts.

If you have decided to go ahead and are looking to buy a telescope, for less than about $200 the best value you will get is a pair of binoculars. Telescopes cheaper than this are, in the main, toys. In general, if this is the extent of your budget, your best plan is to dust off your old binoculars, or borrow some from a friend, and go outside one dark night. Turn off the lights, allow ten minutes for your eyes to adapt to the dark, and start looking.

Get a cheap star map from the newsagents or local camera shop and learn the constellations. Look at anything and everything. The moon is beautiful. Look at it when it's half full. You will see the mountains and craters better then, because the sunlight is falling on them at an angle so their shadows can be seen. Look at stars. There are many double stars that can be split with binoculars. And especially, look at the fuzzy things up there! These will be clusters of stars, or great clouds of glowing gas and dust in space.

Even if your budget does extend beyond the range of binoculars, they are still great value as an introduction to observing the sky. It is worth remembering that any pair of binoculars you might possess are guaranteed to be a hundred times better than any telescope Galileo ever owned.

Stability is vital. Lean the binoculars, or your elbows (or your head), against a post or fence or tree. Your arms will take longer to get tired, and the view will not jump around as you try to hold them steady.

A few nights with binoculars will also help you get an idea of how serious you are about the whole business. If you find the exercise of rugging up to go outside with binoculars tedious, then you need to think again about how likely you are to actually do it with a telescope.

If you've taken the plunge and decided to buy a telescope, the most important thing to remember in the performance of a telescope is size. This is not the length of the tube, but the diameter of the main lens or mirror. Be wary of telescopes advertised as "1000 mm" or "1200 mm". This will refer to the length of the tube. The diameter of the thing is what decides how much light it will catch for you. The pupil of your eye in the dark is about 6 mm in diameter. A 60 mm diameter telescope (or binoculars) has 100 times the area of your pupil, and so it will capture 100 times as much light. A 150 mm telescope will pull in about 600 times as much light as your eye.

Also, don't be fooled by advertisements saying "500x magnification". This is another trap. The maximum magnification of any telescope is twice the diameter of the main lens or mirror in millimetres. So a 60 mm telescope cannot magnify, even theoretically, above 120 times. If you try, all that happens is that the image blurs and you just magnify the blurring (it also makes it dimmer!). In any case, usually magnification isn't actually what you're looking for - it's light-gathering capacity - in other words, diameter again. Most amateur astronomers with quite large telescopes still spend a lot of their time at 50x magnification, or even lower. A lot of interesting things in the sky are not really that small - 50x magnification is plenty - but they are faint. Pulling in the light is the most important thing in a telescope.

So ... bigger is better? Not necessarily! No telescope is any good to you unless you're going to use it. A telescope is no good if it's too heavy to lift, or takes an hour and a half to set up. The main function of this sort of monster will be to gather dust and make you feel guilty for not using it more. Many amateur astronomers have made this mistake. The best telescope for you is the biggest you can reasonably afford, so long as you can lift it and carry it easily.

And, in telescopes even more than binoculars, stability is vital. A telescope's field of view is very narrow, even compared with binoculars, so they come with mounts. It is important that the mount allows the telescope to be swivelled easily from point to point, but most important of all is that it holds the damn thing still when you get there. Even a couple of millimetres of wobble in a telescope mount will make for major frustrations, it has to stay on target and not dance around every time you (inevitably) bang your head on it in the dark, trying to look through the eyepiece.

Happy hunting!