Buying your first telescope is something that, like many things, requires a certain amount of research in order to ensure that you buy the right one for you.
I recently bought my first telescope, and the starting point for me was budget. Browsing around the web it became pretty apparent very quickly that if I wanted to I could spend a lot of money on a telescope, so I set myself a budget of £200 (UK Sterling) – or rather my wife set me a budget of £200!
I knew absolutely nothing about astronomy and telescopes, so I was starting very much from scratch. Having decided on my budget I began to look at what was available for my money.
There are two main types of telescopes: refractors, which uses lenses, and reflectors, which uses mirrors. Being as a lens is more expensive to produce, refractors tend to be more expensive that reflectors. For my budget of £200, it became apparent that if I bought a refractor, I might be a little disappointed. For this reason I decided to go for a reflector. If my budget had been larger, it may well have been a different story.
The most important single factor when assessing how good a telescope is, is its light gathering capability, which is determined by its aperture. This is the diameter of the telescope. Looking at it very simply, a telescope with an 8″ aperture will gather more light than one with a 5″ aperture, and is therefore a better telescope.
It is the eyepiece that, in conjunction with the focal length of the telescope, determines the magnification. The formula to use to work out the magnification is to divide the focal length of the telescope by the focal length of the eyepiece. So, for example, a telescope with a 650mm focal length will produce a magnification of 65 when it is used with 10mm eyepiece (650 / 10 = 65).
The rule of thumb regarding the maximum magnification that can be sensibly achieved with a telescope is to double the aperture (in mm). Therefore, a telescope with a 130mm aperture will have a maximum magnification of 260 (2 x 130).
What I have come to realise in the short time I have had my telescope is that magnification really isn’t that important – getting a nice sharp, bright image is more important, and as you increase the magnification, the brightness and sharpness of the image reduces. The important thing is to experiment until you find the magnification range that works best for your telescope. Mine has a 130mm aperture and I find that magnifications around the x130 to x160 seem to give me the best results. I have tried cranking the magnification up to x260, but it is very difficult to get a good sharp image at that magnification.
However, it is useful to a have a range of eyepieces so you can use different magnifications when you’re viewing an object.
It’s also important to remember that you’ll need to be able to easily move your telescope around, assuming that you don’t have your own observatory! I keep my telescope in the house but I use it outside (as we all should). If it was too awkward to move around I think there would be a possibility that I might stop using it.
I’ve heard it said many times, but it is true, and that is that the best telescope for you is the one that you’ll use the most – there’s no point in buying a great big scope if it’s too much trouble to use it.
About the Author: John Dixon is a web developer working through his own company John Dixon Technology Limited. The company also develops and supplies a free accounting software tool called Earnings Tracker. The company’s web site contains various articles, tutorials, news feeds, and a finance and business blog.