Buying Your First Telescope for Astronomy
A friend asked me a while back for advice on what scope to buy to get into astronomy. So I thought I’d post some details to help anyone else looking for a decent starter telescope. Ultimately it all depends on how much you want to spend really. But when buying a telescope you need to consider 4 things…
The optical tube assembly sits on the mount and the mount is attached to the tripod. As a starter scope I would recommend a “refractor” telescope which uses lenses, mainly because it’s easier to carry about and will take more knocks. The other type is a “reflecting” telescope which uses mirrors which are more delicate and prone to moving. Alternatively there is a hybrid optical system called “Cassegrain” which uses a sealed lens and mirror system. These are ok for starting out but not as robust as a refractor. I believe a good telescope for a beginner is one that gets lots of use and can be taken to a dark sky site. If you already live in a dark sky site and don’t do much travelling, then portability may not be so much of an issue and you might want to consider a larger reflecting telescope that uses mirrors.
The diameter of the lens or mirror is the most important factor. This is like lens aperture in photography… the larger the aperture the more light is collected. For astronomy, larger diameter optics are better for seeing fainter objects and provide more image contrast. My first scope was a 60mm refractor but I quickl
y got bored because I saw everything I could with it fairly quickly. After my own experience, I would recommend a 4 or 5 inch telescope for beginners so you keep it for longer and get more use from it… 4 inches is 100mm, 5 inches is 125mm. You generally see scope diameters advertised in either mm or inches.
Eyepieces fit in the end of the telescope to give different magnifications and fields of view. Ideally you need about 3 different eyepieces to view a wide range of astronomical objects. With focal lengths ranging from 5mm to 25mm depending on the type of telescope and the type of objects you’re interested in. If you look for a telescope starter kit, it will usually come with a selection of lenses suited to the telescope. Alternatively buy from a knowledgeable retailer and ask for their advice on which eyepieces would suit the telescope.
The telescope mount sits on top of the tripod and controls how the telescope moves around the sky. When looking at planets and stars the sky always appears to be moving so things never stay in view very long. This is because the earth is turning round on it’s axis. To compensate for this a computerised mount uses motors to keep the object in view and you can choose things to view on a hand held computer and it will go to the object automatically. These are called “goto” mounts. The other common type of mount is called an Equatorial mount, and is much heavier and not so portable as they use heavy weights. Dobsonian mounts are also not very portable as they are generally very large and bulky. If portability is not a issue, then get the most sturdiest mount you can to hold the optics as it will be more stable when observing.
Like a photographic tripod, a telescope tripod supports the mount and scope. Tripods are all pretty standard and generally come with a mount attached. You could use a photographic tripod you’d have to track the planets and stars manually by moving it yourself. This is only really any good if you have a fluid head on a big video tripod. You could just get a telescope tube to fit on a photographic tripod, but it might be a bit frustrating to use at high magnifications as objects will move about a lot and out of the field of view very quickly. If you have a choice of telescopes, I’d recommend choosing the one with the sturdiest tripod. It may be heavier to carry, but will be more stable when observing.
Unfortunately good telescopes are very expensive like camera lenses due to the optics. Generally the more you spend the better optics and image you’ll get when viewing. For portability you want something that is easy and quick to setup and fairly lightweight to carry about so I would recommend a computerised goto mount. I would also recommend getting a starter kit which includes the telescope, mount and tripod along with a selection of eyepieces. The Celestron Nexstar 102 SLT Refractor Telescope (102mm / 4 inch aperture) recently came top in the Sky At night Group Test for beginners scopes, but there are always new telescopes coming out, so it pays to do some research online. A good sized refractor will last you much longer than a small cheap telescope. It will be good for looking at craters on the moon, rings around Saturn, moons around Saturn & Jupiter, cloud belts on Jupiter, galaxies, nebulae, double stars, globular clusters, and lots more.
I would advise against very small or cheap telescopes, as they will be very poorly made and won’t show you much at all. If you want something cheaper, I would recommend a good pair of binoculars. They will show you craters on the moon and larger objects like Andromeda, bright star clusters, and the millions of stars in the milky way. Something like 10 x 50mm or 15 x 70mm binoculars are good for stargazing. I have a pair of 10 x 50mm binoculars and always take them with me when camping. Sometimes just lying back and looking at the dust lanes and countless stars in our galaxy with binoculars can be just as rewarding as using a large scope.