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Here is a quick look at what’s happening astronomically in December 2013

December 2013 calendar highlighting astronomical events
December 2013 calendar highlighting astronomical events
D. Tondreau

The name for December is derived from the Latin “Decem” meaning “ten”. It was the tenth and last month in the Roman calendar.


New Moon: December 2

Closest to Earth: December 4 (223,735 miles super-size Moon)

First Quarter Moon: December 9

Full Moon: December 17

Farthest from Earth: December 19 (252,444 miles)

Last Quarter Moon: December 25

Planets Visible:

Evening: Venus (look southwest after sunset) and Jupiter (look east after 8pm)

Morning before sunrise: Saturn, Mercury and Mars (look east). Mercury will be visible only for the first week of the month


December 18: The Sun enters the astronomical constellation Sagittarius

December 21: The Sun enters the astrological sign Capricorn


December 7: Earliest sunset for 40 degrees north latitude (Denver)

December 13: second Friday the 13th this year

December 19: Satrunalia, an ancient Roman festival believed to be related to the date we celebrate Christmas

December 21: Winter Solstice 10:11am MST

December 25: Equation of time is zero. (Sundials need no adjustment to account for the variations in the Earth’s orbital speed)


December 13-14: The Geminids peak. Expect 30 to 60 per hour. Unlike most meteor showers Geminids become active around 9pm.Unfortunately there is a bright moon to contend with.

Special Events:

December 1-15: If Comet ISON survives its passage around the Sun it should be visible in the predawn sky. Just how bright and big remains in question.

December 1: Saturn, Mercury, and a thin crescent moon, will form a nice group low on the eastern horizon before sunrise. Comet ISON will be to the left of the group.

December 7: Chamberlin Observatory open house weather permitting. The observatory’s 20” telescope and telescopes belonging to members of the Denver Astronomical Society will be available for viewing. Click here for more information.

December 10: Venus at its brightest

December 25: The Moon near Mars (lower left) in the predawn sky.

December 26: The Moon between Mars (upper left) and Spica (lower left) in the predawn sky. Comet ISON nearest to Earth.

December 27: The Moon near Spica (lower left) in the predawn sky.

December 29: The is next to Saturn in the predawn sky.

Historical Trivia:

December 14, 1546 – Tycho Brahe is born in Knustorp Castle in what was then Denmark. Tycho Brahe was the first astronomer to give extremely accurate positions of stars and planets. Johannes Kepler was a student of his.

December 27, 1571 – Johannes Kepler was born in Baden-Wurttemburg, a small German state. Kepler used Tycho Brahe's star positions to discover the planetary equations that made him famous.

Wishing you clear skies

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