Thursday, 19 January 2012

Buying a telescope? A couple of tips

I see from the Daily Mail that there has apparently been a surge in people buying telescopes as a result of the recent ‘Stargazing Live’ programme on BBC2.
As a bit of a ‘dabbler’ myself (I actually have a minor qualification in astronomy from my university days), I think this is basically a good thing.
However, when it comes to buying a telescope, there’s a couple of tips I’d like to share — and I’d invite others to contribute their own.
First, forget magnification. It’s complicated to explain, but magnification figures can be very misleading when it comes to what you’re going to see down the telescope when you finally get it set up.
Instead, go for ‘width’ — the bigger the aperture, generally the better.
Think of light like water. Imagine its raining and you put a tea cup and a washing-up bowl out in the garden. After twenty minutes, which one’s going to contain the most water? It’s going to be the bowl. Because it covers a bigger area than the teacup, it will have been able to catch more of the rain.
The same with light coming from the sky. A 4" wide telescope will capture not just twice as much light, but four times as much light as a 2" telescope. This means you will see much fainter objects.
But don’t expect to see views like the pictures from the Hubble Space Telescope. With a decent 4" telescope, the Andromeda galaxy — one of the biggest and brightest ‘deep sky objects’ — is still only going to look like a faint fuzzy patch.
On the other hand, the moon and the planets can be quite stunning. But here another rule applies regarding telescopes.
Basically, telescopes come in two kinds: refractors and reflectors. Refractors, you look straight through the tube — think Lord Nelson. Reflectors, you look into it sideways. (There are complicated variations on reflectors, but hey, you’re a beginner, right?)
Due to the way they’re made, reflectors are shorter and they tend to allow big apertures at lower costs. Refractors are longer, and you pay much more, proportionately, for large apertures. BUT refractors give sharper planetary viewing at smaller sizes than do reflectors. So if you want to view the planets — and there’s a lot to see right now — a smaller, quality, refractor might be better than a larger (but not quite large enough!) reflector.
Even so, the rule above still applies — magnification is not the first concern.
The other thing to bear in mind is what you’re going to put the telescope on. If this is your first venture, you’ll probably be OK with a package of telescope and mount, and don’t worry too much about fancy things like motor drives and ‘Go-to’ mounts. Just whack the thing on a tripod, have a look round and if you enjoy it, upgrade when you get bored.
But if you’re reasonably serious about this, look carefully at the mount you’re going to buy. Bear in mind, you can always stick a better telescope on a good mount, whereas a flimsy mount, or an unreliable tracking motor, means even you best viewing efforts will be frustrated.
And another thing — don’t neglect simple binoculars. In fact, for the complete beginner these may be a much better starting point than a telescope.
Personally, I would recommend getting a pair of ‘specialist’ astronomical binoculars. I have a pair of these ‘Revelation’ binoculars from Telescope House. On a limited budget, you would be hard-pressed to do better. They cost me more than the current £55, and they will give you that ‘wow’ factor if you point them at the right part of the sky.
Notice they are 15x70. That is to say, they ‘only’ magnify 15 times (though that’s a pretty big seagull at 100 yards). But they have a 70mm aperture. That’s 2.75 inches — as big as some telescopes. They’re heavy — you’ll get best viewing by putting them on a stand, so don’t forget to buy the tripod adapter as well. But a camera tripod, or even a tall ‘monopod’ will do (it needs to be tall if you’re over 6ft, like me).
Get your kids a pair of these and they will have something that really will last them years, even if they graduate later to a telescope. It is much easier to pack the ‘bins’ and whip them out when needed than to do the same with a 105mm Meade, believe me! (And if you have the money, look at the next size up, though bear in mind that these ‘astronomical’ binoculars are less suitable for daylight work, like birdwatching.)
Finally, much as I appreciate Amazon, this really is a case where I would recommend going to and buying from a specialist suppliers. Telescope House in Tunbridge Wells give a good service in my experience, as do Green Witch (I think it’s a word play on Greenwich, where the Royal Observatory was once located), though they have now moved from their Cambridge location. (Please don’t get their advice then buy from Amazon — that is just wrong.)
Enjoy. But bear in mind, its blooming cold out there.
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