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This Week’s Sky at a Glance, December 21 – 29

Moon crossing Virgo at dawn, Dec 29-31, 2018. By mid-evening the Moon,nearly full, forms a tall triangle with Aldebaran to its upper right and Betelgeuse to its lower right . The Moon, near perigee, shines between the feet of the Castor figure and the dim Club of Orion. Farther left or lower left of the Moon are brighter Castor and Pollux. 

Farther right or lower right of the Moon is Orion, with his belt almost vertical. “The full Moon of December rides higher across the sky in the middle of the night than it does in any other month , “giving luster of midday to objects below. Algol should be at minimum brightness for a couple hours centered on 11:36 p.m. EST. Algol takes several additional hours to fade and to rebrighten. 

Sunday, December 23

Cassiopeia is now a flattened M shape canted at about a 45° angle . Yet hardly more than an hour later, the M has turned horizontal. Constellations passing near the zenith appear to rotate rapidly with respect to the direction “up.”.

Monday, December 24

He’s pretty high now, but his three-star Belt is still nearly vertical. In the other direction, it points down to where bright Sirius will rise around 7 or 8 p.m. to twinkle furiously.

Tuesday, December 25

Procyon, the Little Dog Star, shines in the east about two fist-widths at arm’s length to Sirius’s left. If you live around latitude 30° , these two canine stars will be at the same height above your horizon soon after they rise. If you’re north of that latitude, Procyon will be higher. If you’re south of there,Sirius will be the higher one. 

The eastern edge of the Earth tilts differently with respect to the stars depending on your latitude. 

Wednesday, December 26

Take your time and keep looking. Most people can count 6. With sharp eyesight, a good dark sky, and a steady gaze, you may be able to make out 8 or 9.

Thursday, December 27

Much farther upper left of the Moon is Arcturus, pale yellow-orange. Far to the Moon’s lower left are bright Venus, then Jupiter, then Mercury.


They’re the key to locating everything fainter and deeper to hunt with binoculars or a telescope. Once you get a telescope, to put it to good use you’ll need a detailed, large-scale sky atlas . As dawn arrives, Venus is the brilliant “Morning Star” dominating the southeast. In a telescope Venus is a very thick crescent, waxing from 41% to 45% sunlit this week. 

Saturn is lost in the sunset. Neptune, in Aquarius, is lower in the southwest right after dark and quite a bit more difficult at magnitude 7.9. 


About Alan MacRobert Sky & Telescope senior editor Alan MacRobert has been covering all aspects of astronomy since 1982.

4 thoughts on “This Week’s Sky at a Glance, December 21 – 29”

The rain moved out earlier and now some altocumulus and cumulus clouds in the area. I was able to get out from 2030-2115 EST and enjoy a view of the nearly Full Moon. I used my 90-mm refractor with 32-mm plossl eyepiece and moon filter . Moon 99.4% illuminated. 

I did not see Santa in my 90-mm, 10-inch or 1050 binoculars. However, my wood burning stove is running now. Santa coming down my chimney will have quite a surprise, ho, ho, ho, Rudolf! get me out of here! 🙂.