Monday, Dec. 2, 7:22 p.m. EST
The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the east as a narrow crescent a morning or two before, just before sunrise. It is visible low in the west an evening or two after New Moon.
Monday, Dec. 9, 10:12 a.m. EST
First Quarter Moon
The First Quarter Moon rises just after noon and sets just after midnight. It dominates the evening sky.
Tuesday, Dec. 17, 4:28 a.m. EST
The Full Moon of December is known as the Oak Moon, the Cold Moon, or the Long Nights Moon. It rises around sunset and sets around sunrise, the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky. This will be the smallest full moon in 2013.
Wednesday, Dec. 25, 8:48 a.m. EST
Last Quarter Moon
The Last Quarter Moon rises around midnight and sets around noon. It is most easily seen just after sunrise in the southern sky.
Sunday, Dec. 1, before sunrise
Saturn, Mercury, and the Moon
On the morning of December 1, half an hour before sunrise, the 28-day-old crescent Moon will be flanked by the planets Saturn and Mercury: Saturn above and Mercury below. Seeing this will require a low southeastern horizon, very clear skies, and careful timing: before the light of dawn erases the view but after the three objects have risen sufficiently to clear horizon mists. Half an hour before sunrise should be about right, and binoculars will help.
Friday, Dec. 6, 2 p.m. EST
Venus at greatest brilliance
When Venus is fully illuminated, it is on the far side of its orbit, and so is dimmed by distance. When it is closest to Earth it is lit from behind, so also dim. Today is the “just right” point in its orbit where distance and angle of illumination balance to present the greatest possible illuminated area, and hence its brightest light. At magnitude –4.9 it outshines everything in the sky except the Sun and Moon. If you look 7 degrees below the Moon on the previous afternoon, Thursday Dec. 5, you should be able to easily see Venus in the daytime sky.
Saturday, Dec. 21 12:11 p.m. EST
The Sun halts its southward migration and pauses briefly before moving north again. This is the shortest day of the year, followed by the longest night. As happened last year (and every year) the Sun will be close to the direction of the center of the Milky Way, and once again the World will not end.
Wednesday–Sunday, Dec. 25–29, 10:08–10:14 p.m. EST
The Moon goes visiting
Over the next five mornings, just before dawn, the Moon will pass by two planets and a bright star. It will be just west of Mars on Christmas morning:
Between Mars and Spica on Dec. 26:
Just east of Spica on Dec. 27:
Just west of Saturn on Dec. 28:
And just below Saturn on Dec. 29:
East and west in the sky are the reverse of east and west on Earth maps because we are looking up rather than looking down. Notice how the Moon’s crescent shrinks over the five mornings, and how the stars and planets rise 4 minutes earlier each morning.
Mercury is well placed in the morning sky for observers in the northern hemisphere for the first ten days of December.
Venus is at greatest brilliance on December 6, low in the southwestern sky just after sunset.
Mars continues to brighten in Virgo in the morning sky.
Jupiter rises in the northeast about an hour and a half after sunset and shines brightly in Gemini the rest of the night. The Great Red Spot is easier to see than in many recent years, showing a distinct orange color.
Saturn is low in morning twilight all month long, in the constellation Libra.
Uranus is visible all evening, setting around 1 a.m. It spends most of the month in Pisces, but makes a brief excursion into Cetus from Dec. 10 to 20.
Neptune, in Aquarius, is visible in the early evening and sets around 10 p.m.
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