Orbital diagrams for the inner planets December 2008 to March 2009, April to July 2009, July to November 2009, November 2009 to March 2010 and the outer planets for 2009.
| Date (NZDT) | Diary of Solar System Events in December 2009 for New Zealand |
| December 2 | Uranus stationary. |
| December 2 | Full Moon at 8:30pm NZDT (07:30 UT). |
| December 3 | Moon furthest north, resulting in the lowest southern hemisphere transits for the month. |
| December 5 | Moon at perigee, its closest to the Earth for the Lunar month, 363480 km. |
| December 8 | 65% lit waning Moon 3° to upper left of Regulus, magnitude 1.4, brightest star in Leo, morning sky. |
| December 9 | Moon at last quarter 1:14p6am NZDT (00:14 UT). |
| December 10/11 | 42/32% lit waning Moon 9° from Saturn, morning sky. |
| December 12 | 22% lit crescent Moon 2.5° above Spica, magnitude 1.1, brightest star in Leo, morning sky. |
| December 16 | Moon furthest south, resulting in the highest southern hemisphere transit for the month. |
| December 17 | New Moon at 1:02am NZDT, (Dec 16, 12:02 UT). |
| December 18 | Very thin crescent Moon 2° below Mercury
early evening sky.
Mercury at greatest elongation, 20° east of Sun. |
| December 21 | Moon at apogee, its greatest distance from the Earth for the Lunar month, 405729 km. |
| December 21 | Jupiter 0.5%deg; from
Neptune
20% lit waxing Moon 4° below Neptune and Jupiter. |
| December 22 | Mars stationary. |
| December 22 | Southern summer solstice; sun furthest south just before 7am NZDT. |
| December 25 | Moon at first quarter 6:36am NZDT (Dec 24, 17:36 UT). |
| December 25 | Pluto at conjunction, 5° from Sun. |
| December 26 | Mercury stationary. |
| December 30 | Moon furthest north, resulting in the lowest southern hemisphere transits for the month. |
| 2010 January 1 | Full Moon at 8:13am NZDT (2009 Dec 31, 19:13 UT). Penumbral eclipse not visible from NZ |
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MERCURY is in the early evening sky during December. It sets about
90 minutes after the Sun in the middle part of the month. This will make the planet visible
low towards the southwest 45 minutes or so after sunset, although the prolonged twilight
of midsummer may hinder observation.
Apart from the first two days of December when it will be in Ophiuchus, Mercury will be in Sagittarius. On December 10 it will be only 20', of the-thirds the diameter of the full moon, from the 2.8 magnitude star λ Sgr. From December 12 to 14 Mercury will be below the handle of the "teapot", and just under 1.5° below σ Sgr, Nunki, magnitude 2.1 on the latter date. Mercury will be a lot brighter, magnitude -0.5.
Mercury will be at its greatest elongation, 20° east of the Sun, on December 18. At the same time the very thin crescent Moon, only 3% lit, will be 2° below the planet. After elongation the Sun will start closing in on Mercury. Then on December 26 Mercury is stationary following which it will start moving to the west through the stars and towards the Sun. By then the planet will set just over an hour after the Sun and become lost to view in the evening twilight.
VENUS will be only 10° from the Sun at the beginning of
December, rising less than half an hour before it. The planet will be less than 4° up at
sunrise, making it difficult to observe.
During December, Venus slowly closes in on the Sun, so that the two are only 2.5° apart by the end of the month, too close for observation.
MARS continues as a morning object during December, although by the
end of the month it will rise a little before 12 midnight. It will also brighten during the
month from magnitude -0.1 to -0.7 so making it slightly brighter than Canopus, the second
brightest star.
The planet is stationary on the night of December 21/22 after which it will start to move to the west through the stars, an apparent motion due to the faster moving Earth beginning to catch up with Mars in their orbits.
Mars will be in Leo all month, a little over 10° to the left of the brightest star, Regulus. On the morning of December 7, the 76% lit waning Moon will be about 6° to the upper left of Mars.
JUPITER'S easterly movement through the stars will take it past
Neptune for a third conjunction with the outer planet this year. The two will be slightly over
half a degree apart, the diameter of the full moon, on December 21. And that evening the Moon
will be only 4.5° below the two planets. However the Moon will be a crescent, 20% lit,
not full.
Both planets will remain in Capricornus all month. By the end of December Jupiter will set a little before midnight for almost all of New Zealand, except in the far south where it will set just after midnight. Thus the best time for observing the planet will be as soon as the evening sky darkens.
SATURN will remain a morning object throughout December. At the
beginning of December it will rise close to 3.00 am in Auckland and about half an hour later at
Invercargill. By December 31 Saturn will rise some two hours earlier and be easily visible, at a
moderate altitude to the northeast, an hour before sunrise.
The planet will be in Virgo, about 20° from Spica. The Moon will be about 9° from Saturn on the mornings of 10 and 11 December; with the Moon to the upper left of Saturn on the 10th and to its upper right on the 11th.