WHAT'S UP: Telescope buying tips

Nov 18, 2011

 

But unless you know what you’re doing, you are at the mercy of marketers and you might not make the best choice.

First and foremost, when considering one telescope or another, don’t read anything about magnification.

Oh, and even before that, don’t buy a telescope from a retail outlet. Telescopes offered for sale at local department stores are generally of very poor quality. Shop online from a reputable merchant.

Secondly, don’t read anything about magnification. Yes, I know, I just wrote that four sentences ago. It is so important I wrote it again.

Most people think telescopes are best at making distant things appear closer (or bigger). But the fact is, telescopes are better — much better — at making faint things appear brighter.

One way you might go about selecting a telescope is to decide two things at the outset: How much are you willing to pay, and what do you think you (or the lucky recipient) will use it for?

Nowadays, you can get plenty of telescope for backyard observing for less than $200, and maybe even as little as $100. Of course, you can always pay more, a lot more, to get “more” — but that is why you have to imagine the telescope in use.

If the telescope is for a child, consider ease of use first and foremost. Sure, a 10-inch-diameter scope makes great images of distant galaxies, but it will weigh 50 or 100 pounds, and will stand 4-5 feet off the ground.

If the telescope is for an adult, consider its likely use. Sure, a $5,000 APO refractor is a fine optical instrument, maybe even a status symbol — but for looking at planets and star clusters in the backyard, it is likely overkill.

Telescopes with widely varied optical designs are available — from simple Newtonian reflectors, to achromatic refractors, to complex catadioptric scopes.

Telescope mounts run the gamut from simple alt-azi mounts (like camera tripods), to tilted and counter-balanced equatorial mounts, to motorized/computerized systems.

It’s all a bit too much.

In my honest opinion, the K.I.S.S. principle always applies (K.I.S.S. = keep it simple, stupid!). If you are thinking of buying a telescope, buy the best telescope on the sturdiest mechanical mount you can afford. Don’t be impressed by computerized mounts and extras like software and carrying cases.

Look for things the marketers don’t highlight.

Does the telescope have a nice finder scope? Laser or “red dot” finders are really nice, and make aiming the telescope a breeze.

Does the telescope have a nice focuser?

Does the telescope include a sturdy mount? Aiming a telescope to capture a distant ray of light and holding the telescope steady to appreciate the view is key. A cheap, wobbly mount just won’t do.

With regard to size, there are two numbers to consider: aperture and focal length. Aperture is the diameter of the main lens or mirror of the scope. Bigger is better; as big as you can afford (without getting “aperture fever”). Look for something at least 3 inches in diameter.

Focal length relates to — I hate to say it — magnification. With a given eyepiece, a telescope with a longer focal length magnifies more. Stay away from long focal-length telescopes; especially ones with small diameters.

The Shoreline Amateur Astronomical Association (holland-saaa.org) is hosting a program called “Buying a Telescope and How They Work” on Saturday at Hemlock Crossing County Park in West Olive, beginning at 7:30 p.m.

And, as you ponder all this, keep this in mind: The best telescope is one that gets used.

— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com.

 

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