DURING this time of year, I am often asked about telescopes as gifts. While a good quality telescope will bring a lifetime of discovery and enjoyment, purchasing the right one can be a confusing task if you’re unfamiliar with them and their functions.

First and foremost, a telescope’s main purpose is to gather light. Telescopes accomplish this through the use of lenses and/or mirrors. The size, or aperture, of a telescope’s lens or mirror determines its light gathering power and maximum magnification potential. There are three basic types of telescopes known as refractor, reflector and catadioptric. Refractors use lenses to gather light and have the classic long tube design. They are the most durable of the three types. Reflectors use mirrors to gather light. They are the least durable but also the most cost effective for their size. Catadioptric telescopes use combinations of lenses and mirrors and are a good balance of refractor and reflector but also come with a higher cost.

Newer telescopes are computer controlled and are known as “GoTo” telescopes. A hand controller, much like a television remote control, is used with this type of telescope. After setup, a GoTo telescope will automatically find astronomical objects selected by the user. This is much easier than the old manual method of locating objects, but a basic understanding of the night sky is still beneficial when using GoTo telescopes.

Don’t forget that a telescope’s mount and tripod are essential to its operation. An equatorial mount, used for tracking astronomical objects, is the best type. In addition, ensure the tripod is sturdy and solid because a cheap tripod will cause the object in the field of view to move and shake with any little vibration or breeze. Also, avoid telescopes with large magnification claims such as 500x. Magnification is limited by atmospheric conditions and the telescope’s aperture. Whichever telescope you choose, NEVER point it at the sun as immediate and permanent eye damage can occur.

Ultimately, the best telescope is the one that is easy to set up and use, even if it is a smaller model. From light polluted urban skies, you’ll be able to view the moon and planets in detail along with some of the brighter deep sky objects for year-round enjoyment after the holidays.

DECEMBER SKIES

Brilliant Venus becomes easier to spot in the evening sky this month. Watch it and much dimmer Saturn pass each other above the southwestern horizon between the 7th and 15th. The moon will join Venus on the 28th for a very pretty pairing.

The winter solstice begins on the 21st with the shortest amount of daylight and longest nights of the year.

David Abbou of Stafford County is a volunteer for the NASA/JPL Solar System Ambassadors Program and is a member of the Rappahannock Astronomy Club. Contact him at davidastronomy@comcast.net.

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