Bad Astronomy

Hazards of Cheap Telescopes

I wonder how many people have bought a small telescope for £100 or so, have been unable to work it, or find that it does not perform as advertised, and then dumped it in the attic. There is of course nothing wrong with small telescopes (although I prefer binoculars myself), provided one gets good advice and buys from the right people. Who are the "wrong" people? Phil Plait, an Hubble Space Telescope astronomer who comments regularly on "bad astronomy" (see his web page at www.badastronomy.com), recently watched a TV show aiming to sell a three-inch reflector, and he became "boiling mad" at the "gross incompetence" and "lies" of the show's presenters. There were two of them, a rep from the company selling the telescope and a "gushing" TV person. First they showed a brilliant picture of the Whirlpool Galaxy (M51) and said this was how it would look through the three-inch scope!

Get good advice and buy from the right people

Plait found this outrageous. M51 is a faint object with a magnitude of 8, and nobody could "see" it through this instrument. One would need a camera to collect the light very slowly as well as an electric motor to keep the scope on its target. (Even then M51 would be just a faint smudge.) There was no suggestion that any such equipment was being given away free. Worse was to come. "Pluto is no problem for this telescope," gushed the TV person, and the company rep nodded agreement. This, said Plait, was a "complete bald-faced lie" With a magnitude of about 13.5, Pluto is 400 times fainter than the faintest naked eye star. Seeing it "takes a very high quality telescope, extraordinary viewing conditions and a lot of experience behind the eyepiece." Now well into their stride, the pair claimed that the three-inch was as good as Hubble itself I swear I'm not making this up. It is a lunatic statement. If an instrument one can carry beneath one's arm is as good as Hubble, why would someone have spent billions of dollars putting Hubble in orbit? To "prove" it, the pair showed several high quality images which they said were taken by Hubble, with the implication that the threeinch could do just as well. But they weren't even Hubble pictures. One of them was a wide-angled shot of the Milky Way, which Hubble's narrow-field camera couldn't have taken. It had a crosshair in the print, and Plait, as one who uses Hubble daily, assures us that real HST pictures never display this. If you fall for all this nonsense, ``you deserve to get bilked out of a hundred bucks." The truth (as I understand the matter from Plait) is that one should never buy a cheap telescope by itself. One needs lots of extras including several lenses. A telescope with a single lens is about as useful as a piano with one key. It should also have a tripod and perhaps a camera attachment, not to mention a star chart or some kind of guide to the heavens. And a pair of 7x50 binoculars performs as well as a cheap scope without needing many extras. I hope I don't sound biassed in pointing this out.