December sky shines brightly

Posted: Sunday, December 01, 2002

Christmas is upon us and the best astronomy buy is a starfinder, which costs between $3 and $10. It's also called a planet locator or planisphere, and it is a piece of cardboard with a dial that shows the stars in the sky for any given day, time and year.

I didn't see any at local stores, but you can e-mail me at aveh@uaa.alaska.edu and I'll tell you where to order one. Some novelty and nature or science stores in Anchorage should carry them.

For the budding astronomer, this starfinder and a pair of binoculars is a much better investment than a telescope. I already have seen telescopes at various department stores in the area that advertise a 420x magnification. You can actually use them for looking at the moon or see Jupiter's moons (appearing as dots). But binoculars would be just as good.

I know, this is a really tempting gift to present to a youngster, but I have selfish reasons to ask you to think about it first: 1) I want people to enjoy astronomy, 2) I don't want anybody to get frustrated by a wobbly telescope that produces blurry images, and 3) if you keep enjoying astronomy, it benefits me by having a larger audience of like-minded people.

Two things you have to look for when you want to buy a telescope: a stable mount for the telescope, and that the finder scope is aligned with the telescope. My advice is buy a starfinder and stay with the binoculars that you perhaps already own. If you really want a good telescope, call me or stop by my KPC office and we can talk about it.

As for what's up in the sky to see, Venus is the bright object in the east predawn sky.

The moon will be full Dec. 19.

Mars is low in the southeast before sunrise.

Another bright planet will join Saturn in the evening sky this month: giant Jupiter. The accompanying diagram will help you find Jupiter above the eastern horizon after 10 p.m. early this month and after 8 p.m. late this month But Jupiter is way brighter than all the stars around it, so you actually can use it to find the constellations of Cancer and Leo.

Use binoculars to look for Jupiter's moons. Again, look for Saturn. From Cancer and Leo go west to Gemini and Taurus. In the southeast you'll find the constellation Orion, the star cluster Pleiades (Seven Sisters, right from Saturn), and many bright stars -- Sirius, Procyon, Aldebaran, Castor, Pollux and Capella.

Check them out on your starfinder. On the back it usually lists the planet positions for the next four years. Also, see last month's diagram or check out Astronomy and Sky and Telescope magazines at the Kenai Community Library and at various stores (I've seen them at Fred Meyer, Kmart and Carrs).

This month also marks several benchmarks for daylight: the earliest sunset occurs at 3:53 p.m. on Dec. 15; the latest sunrise is at 10:14 a.m. on Dec. 27. These slight differences are due to Earth's tilt of axis, which makes a day-night cycle an average 24 hours, and the exact dates for these benchmarks depend on latitude.

I will explain the exact reasons in an upcoming column. But, as expected, the shortest day lasting 5 hours and 41 minutes is on the winter solstice, Dec. 21. On that day, the sun will ascend to a whopping 7 degrees (90 minus latitude of 60 minus axis tilt of 23 on the winter solstice) above the southern horizon at around 1 p.m. locally.

On Jan. 3, we will have our closest approach to the sun at 91.6 million miles, compared to an average 93.1 million miles. I will talk about that next month.

Andy Veh is the physics and astronomy instructor at Kenai Peninsula College. This column will appear on the first Sunday of each month. He can be reached at aveh@uaa.alaska.edu.



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