Rising during the evening this month is the planet Jupiter, my oldest friend in the night sky. Back when I was perhaps barely a teenager, a friend received a small telescope for Christmas. He set it up on his driveway and we naturally pointed it to the brightest thing in the night sky, not knowing what it was. We focused in on the disk of a planet and noticed a few stars lined up close to it. Over the next few nights we would see the positions of these stars change we had unwittingly recreated Galileos discovery of the four largest moons of Jupiter.
The telescope we used was one of the typical, inexpensive models sold at most big-box stores. It had a 2-inch diameter lens at the front to gather the light and a mount that allowed you to move it up and down and right or left.
This kind of telescopes natural habitat is the garage, basement or attic.
With Christmas approaching, we should take caution against sending more of these scopes to their doom. What should you buy and why?
There are two important criteria for choosing a telescope and neither of them is the magnification, often touted on its box. Other than at the best observing sites (not here), you will rarely be able to use a magnification of more than a couple hundred. More often you will use 50 to 100, and it is changeable by changing eyepieces, which are a standard size and readily available.
What is important is the diameter of the main lens or mirror that collects the light, and the type of mount. The larger the optics, the more light you collect and the brighter the image is. And, to a limit, the more detail you can see. The sad fact is that for telescopes, there is no equivalent of a nickel cigar: Optics are expensive to make.
Also, after you look at the bright planets and moon with the cheapo scope, its mount will prove frustrating to use to find things you cannot see with the naked eye. For about $500 you can get a 4-inch diameter scope that is computerized and points itself.
For parents and spouses of potentially budding astronomers, I recommend starting with a good pair of 10x50 binoculars. They will show a lot of the sky, including the moons of Jupiter. If interest builds, you can then get a good starter scope. If not, you have binoculars for other uses.
Daniel B. Caton is a physics and astronomy professor and director of observatories at Appalachian State University. Email: email@example.com. More on this months column: www.upintheair.info.