The traditional full moon name for December is the “Cold Moon”. Other common names include the “Oak Moon”, “Christmas Moon” and the “Long Night Moon”. “Moon before the Yule” applies when the full Moon comes before Christmas. The Lakota Sioux called it the “Moon of the Popping Trees”. The Cheyenne named it the “Big Freezing Moon”. The Taos call it the “Night Moon” and to the Wisham it is “Her Winter Houses Moon”.
The name for December is derived from the Latin “Decem” meaning “ten”. It was the tenth and last month in the Roman calendar.
Technically the full moon is only a moment in time. For December that moment occurs at 3:22am MST on Friday December 28. The Moon will look full on the evenings December 27, 28, and 29. So which is closest to the true full moon? There is an easy way for the casual observer to tell. A full moon always rises opposite the setting Sun. In general, the Moon that rises within a half hour of sunset is closest to the full moon. If the Moon is well above the horizon or has not risen until well after (greater than a half hour) sunset, it is not a full moon even though it looks like one. Let’s see what the data shows this month for Aurora, CO.
December 27 The Moon rises within 30 minutes of sunset
Sunset: 4:41 pm MST
Moonrise: 4:28pm MST
Difference: 13 minutes (Pass, Moon and Sun are not opposite)
December 28 The Moon rises after sunset
Sunset: 4:42pm MST
Moonrise: 5:22pm MST
Difference: 40 minutes (Fail, just barely, Moon and Sun are opposite)
December 29 The Moon rises well after sunset
Sunset: 4:42pm MST
Moonrise: 6:19 pm MST
Difference: 1 hour 37 minutes (Fail, Moon and Sun are not opposite)
This test works “most” every time for any full looking moon. The Moon will be closer to full on the evening of December 27 (10 hours 54 minutes before full) than on the evening of December 28 (14 hours after full).
A full moon is the only time the Moon is up all night and the only time a lunar eclipse can take place as it did last June. A full moon also sets in the west opposite the rising Sun providing us living near the front range really neat moonsets over the mountains, easily noticed by early morning west-bound commuters.
The December 28 moonset (7:16am MST) will occur a few minutes before sunrise (7:19am MST). The December 29 moonset (7:55am MST) occurs after sunrise (7:19am MST). You want to start watching before 6:45am MST and 7:30am MDT respectfully. If you have the time, observe the sunrise. They are usually pretty good here in Colorado.
Wishing you clear skies