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What's Up?

Every month, the Royal Astronomical Society of NZ (RASNZ) issues information about what solar system objects are viewable for the month.  We will update that information here to share with you as it becomes available.

December 2013

Phases of the moon (times as shown by guide)

 New moon: December 3 at 1.23 pm (00:23 UT) 
 First quarter: December 10 at 4.12 am (Dec 9, 15:12 UT) 
 Full moon: December 17 at 10.28 pm (09:28 UT) 
 Last quarter December 26 at 2.48 am (Dec 25, 13:48 UT) 

The planets in December

Venus starts December high and prominent in the evening sky, but will steadily lose altitude during the month as it moves towards conjunction early in 2014. Jupiter will become visible in the late evening. 
Jupiter will also be visible in the morning sky, while Mars will rise some hours before the Sun. Saturn will emerge out of twilight during December, but Mercury will be too low in the dawn sky to see. 
VENUS, the evening planet. December sees the virtual disappearance of Venus from the evening sky. At first it sets more than 3 hours after the Sun, just after midnight (NZDT) for much of New Zealand. In the early part of the month it will remain readily visible quite high to the west shortly after sunset. As the month progresses the planet´s elongation from the Sun rapidly declines so it will get lower in the sky and set earlier, so that by the end of December it will set less than an hour after the Sun. 
JUPITER will be visible for much of the night by the end of December, rather low to the northeast in the evening. It rises shortly before 
midnight in New Zealand at the beginning of the month, but gets steadily earlier to rise only a few minutes after sunset by the 31st. From New Zealand the planet will remain a low object due to it being well north of the celestial equator. 
MARS moves higher into the morning sky during December. It rises about 3 hours before the Sun on the 1st and four and a half hours earlier by the 31st. The planet is close to the celestial equator so will get higher than Jupiter. It brightens slightly during the month from magnitude 1.2 
to 0.9. 
SATURN moves out from the Sun into the morning sky during the month. It rises about 1 hour before the Sun on the 1st and 3 hours before it on the 31st. At first in December it will be low and difficult to see. By the end of December the planet will be readily visible before dawn about 20° above the horizon to the east. 
MERCURY rises little more than half an hour before the Sun early in the month, making it virtually impossible to see. It closes in on the Sun 
during the following 4 weeks to be at superior conjunction at the far side of the Sun on the 29th. 
OUTER PLANETS Both Uranus and Neptune are principally evening objects during December. Uranus at magnitude 5.8 is stationary on the 18th and spends the month on the border of between Pisces and Cetus. It sets well after midnight, about 3.30 am on the 1st and 1.30 am on the 31st.  Neptune is at magnitude 7.9 and is in Aquarius. It sets about 90 minutes before Uranus.

Brighter asteroids

(1) Ceres and (4) Vesta are both morning objects in Virgo a few degrees from one another and a few degrees from Mars. The three form a rough line with Vesta in the middle. Ceres will be to the lower right of Vesta and Mars to its upper left. The two asteroids are 6° apart at the beginning of December, 5° at the end of the month, when Vesta will also be 8° from Mars. Ceres is at magnitude 8.7 to 8.6 during December while Vesta brightens a little more from 8.0 to 7.7. Both will be readily visible in binoculars, their changing position compared to the stars visible from night to night. 
(2) Pallas is in Hydra and brightens during December from 8.5 to 8.0 so similar in brightness to Ceres and Vesta. It rises just before 11 pm at 
the beginning of December and about 9.30 pm by the month´s end. 

-- Brian Loader