NEWS

Looking Up: Telescopes narrow the view but broaden your horizons

Peter Becker

The joys of viewing the night sky are enhanced if you have a telescope and know how to use one. And clear skies help, of course! Once the clouds depart, a great window opens, allowing you to witness the universe beyond, exploring the realm of stars and galaxies, without ever leaving your yard.

You don’t need a telescope to appreciate the sky; in fact, sometimes eyes alone will suffice. Binoculars (which are really two small telescopes attached to each other) bring out a great deal more, letting you examine a little more closely the grand canopy of stars you have been feasting with your unaided eyes.

Telescopes greatly narrow your field of view. Instead of beholding the vastness spread out from your right to your left, you close in on a very small spot. Eyes alone allow you to see over half of the entire sky at once, available to you at any one time. The sky above, which is referred to as the “celestial dome” and is like peering inside an upside-down bowl, measures 180 degrees from one side to the other.

Binoculars narrow that field to about 7 degrees, or a bit more than the angular distance between the front stars of the Big Dipper. A telescope magnifying at least 30x diminishes that field of view to about 1 degree, or less depending on the magnification you select by switching eyepieces. The moon is about one-half degree in angular width.

That makes pointing a telescope a challenge. Backyard telescopes will have either a tripod or a pedestal. Be sure you have a steady one, and set it on a level surface. Wooden decks are fine only if you stand very still when using the telescope; the least vibration will send your magnified image bouncing all over.

Your little “finder” scope attached to the main telescope tube needs to be properly aligned. This is so the star or planet or other object you are trying to see, will be seen with your main telescope when it is centered in the finder view. The finder scope has a broader view, like binoculars, allowing you to locate your target by matching star patterns you see, with the plotted star patterns on a good star chart or star atlas. It is easier to align the finder in the daylight, so you can see what’s around the test target to hunt it down (use, for example, a distant church steeple or chimney; don’t do this with that bird you see resting on a wire, unless you’re VERY quick!).

Begin with low magnification that has a wider field of view. Low-power eyepieces may have a field of view of about a degree. If your targeting is a little off, you still might have that star or planet in sight in the low power view, albeit a bit off-center.

You may then switch to a higher power eyepiece, being careful not to knock the telescope even slightly. You will have to refocus your instrument. Higher magnification allows a closer look, but your star or planet will run away on you quicker! The whole sky appears to revolve around you east to west, as Earth turns around. The more magnification you use, the more pronounced is this affect.  Some telescopes use a motor drive to track the star or other target; you may also have a slow-motion control to gradually shift the telescope with the turn of a wheel to keep the target in sight. Once you get used to it, gentle nudging of the telescope tube will allow you to track it yourself, though it is more of a challenge at high power.

Here are a few more tips. Never touch the lens or mirror with your fingers, and clean them as carefully as you would your eyeglasses. Too much cleaning is worse than too little, due to the risk of scratching.

If you have a reflector telescope, the air inside the tube needs to escape before you will have the best views especially at higher magnification. This is because moving a reflector from a warm house into the cold night air causes the warm air in the tube to flow out. This causes air turbulence, and your higher-power images, needed for detailed look at planets and the moon, will tend to shake, especially if the night is very cold. It is better to put the reflector outside for an hour or more before you venture out.

When storing it inside, be sure to cap the telescope lens or front of the reflector tube, to keep out dust. You may get some dust outside over the course of many nights of use. More interesting is when a firefly gets inside in the summer months -- this happened to me. Then there’s the story of someone’s kitten that got inside the tube.

Many telescope companies put out very fine telescopes for beginners as well as those more advanced in the hobby. Among them are Orion Telescopes & Binoculars, Meade and Celestron. They have Web sites, and their companies as well as others advertise in such popular periodicals as Sky and Telescope or Astronomy Magazine.

New moon is Oct. 28; watch for the crescent in the west after sunset following that date, along with Venus in the west and Jupiter low in the south-southwest.

Keep looking up!

Peter W. Becker is managing editor at The Wayne Independent in Honesdale, Pa. He has been an amateur astronomer since the age of 12, in 1969. He may be reached at pbecker@wayneindependent.com.