Telescopes: Bad Gift Idea!
So, Santa brought you a shiny brand new telescope for Christmas. Boy, are we gonna have some fun now! What? You don't know the first thing about telescopes - even less about the night sky and astronomy in general. Well, it's a mighty good thing that you're reading this column.
I hate to bring this up again, but I get a ton of E-mail on a regular basis. And I answer every inquiry as best I can. Typically, it's from beginners and novice Astronomy enthusiasts looking for some advice on everything from how to "turn on" their telescopes, to what it was they saw in the sky last night. During the past few months, I've been answering a lot of questions about meteor showers and the like. Most recently, however, the Christmas Gift questions have been prevalent. Here's a typical request.
Dear Mr. StarMan, (my online persona)
I'd like to buy my son (daughter, husband, wife, uncle, some guy down the street) a telescope for Christmas. I don't know anything at all about astronomy or telescopes. Could you suggest a telescope I should buy? I'd like to spend no more than $200.00. Thank you in advance for your help.
Here's what most of these inquirers receive in response.
DON'T buy a telescope for someone as a gift. Especially if you and they have no experience with telescopes and/or astronomy. Rather, look into getting them a few books on the subject. A subscription to Sky & Telescope or Astronomy magazine make ideal gifts for wannabe amateur Astronomers. I know of a really great book for beginners. It's in book stores everywhere. It's called The Lawnchair Astronomer, and it makes a great stocking stuffer too!
From there, I often send them via hyperlink to an online FAQ (Frequently Asked Questions) file dealing with all the specifics of telescope purchasing, owning and operating. As much as I could, I've discouraged folks from blindly buying telescopes as gifts or even for themselves, until they learn a little about astronomy and what telescopes are all about. For those who may not have gotten this advice, and/or for those who've ended up owning that shiny brand new telescope, here are a few things that you should know.
Size Matters: The main factor determining how well a telescope will perform is its size. Specifically, the size of an instrument's objective lens or mirror will determine what kinds of objects the instrument will be able to resolve. An astronomical telescope's main priority is to detect light. How dim an object that a telescope can detect is directly related to its "light gathering" ability. The larger the telescope's primary objective is, the dimmer an object it will be able to resolve.
Celestial objects are classified in several ways. One of these is related to its apparent brightness. The average brightest stars in the sky are classified as magnitude 1. The dimmest stars, those just at the limit of naked-eye visibility, are classified as magnitude 6, with those remaining stars inbetween the brightest and dimmest as magnitudes 2, 3, 4 and 5. All these are the stars that you can see with your eyes alone. Dimmer stars, magnitudes 7 and dimmer, require some type of optical aid to resolve. Here is where binoculars or telescopes come into play. The larger the instrument, the dimmer the magnitude of object a telescope will be able to detect. Developed by an ancient Greek Astronomer by the name of Hipparchus, this magnitude system works in the opposite direction as well. For objects brighter than magnitude 1, a negative integer is used - e.g. magnitude -1, -2, etc. The sun, moon, the brighter planets and some of the very brightest stars are classified in this way.
Quality and Types: Telescopes come in two basic designs: Refractors and Reflectors. (See Graphic - Figure 1) Reflectors also come in numerous configurations. The most common small telescopes are the refractors. These gather and focus light via a primary lens which directs the light path down its tube to a focussing secondary lens on the other end of the tube where the image may be magnified. This is the basic ship captain's spyglass design. Telescopes of this type are best suited to observations of the moon, bright planets, stars and the very brightest deep-sky targets.
The Lawnchair Astronomer
Gerry Descoteaux is the author of “The Lawnchair Astronomer,” a Dell Trades paperback. He has been writing about astronomy for more than 25 years. He also played an integral role in the development of America Online’s pioneering distance education program known as AOL’s Online Campus and served as Professor of Astronomy there for 10 years. He can be reached at TheStarMan@thelawnchairastronomer.com.
Notes From the Lawnchair