Telescopes, some thoughts…
I was walking past a typical high street department store yesterday when my attention was grabbed by a telescope in the window. It was only about 10cm in diameter (about 4″), was on the market for a whopping £199.99 and boasted a magnification of 750x. With winter approaching for those of us in the northern hemisphere and Christmas hot on its heels its timely for a reminder not to be sucked in by ridiculous claims of equipment like this.
The rule of thumb is this; you can work out the maximum useful magnification of any telescope by multiplying its aperture in inches by 50. For the telescope above, its useful maximum magnification is 4 multiplied by 50 giving 200x. Anything more than this will only be possible with superb quality optics (and you can be sure a telescope costing £199.99 won’t have them) and under exceptional observing conditions. The telescope in question probably did have eyepieces to give a magnification of 750x but the image would be appalling.
If you are thinking of buying a telescope or buying one as a gift for Christmas then my advice is simple. If its for an adult then save your pennies and get hold of a decent pair of binoculars which will still show you some great views. They won’t give a great image of planets though as at least 20x magnification is needed to reveal them in detail. A good pair would be 10×50 and you will start to learn your way around the sky. Its better to do this to see if you really are getting into the subject and get a good quality telescope later than waste money on a poor one now and destroy any spark of interest you may have.
My advice for children is different, they don’t have quite the same needs as an adult so I would actually suggest getting them a cheap telescope. The image will be poor and the quality of the instrument not great but it will more than likely still inspire them. I was first interested in astronomy as a ten year old and, had I been bought a pair of binoculars would have been really disappointed. A telescope is the real deal for children, get them a cheap one and they will be happy.
When you do get round to buying a telescope, a great starter instrument will cost around £400. This will give you a decent sized aperture, around 15cm (6″) and a good sturdy mount. Search out ‘dobsonian reflecting telescopes’ (like the one pictured above) to find suppliers near you and you will be treated to amazing views of the Universe.
Follow this link for more detailed advice on Choosing Telescopes