December Calendar by Dave Mitsky

All times, unless otherwise noted, are UT (subtract five hours and, when appropriate, one calendar day for EST)

12/1 Last Quarter Moon occurs at 12:44; Saturn is 2 degrees north of the Moon at 13:00
12/4 Mercury is at the descending node today
12/5 A minimum lunar libration of 6.1 degrees occurs at 1:00
12/6 Venus is 7 degrees north of the Moon at 1:00; the Moon is at apogee, subtending 29'33" from a distance of 406,235 kilometers, at 16:53
12/8 The earliest sunset of 2007 at 40 degrees north latitude occurs today
12/9 New Moon (lunation 1051) occurs at 17:40; a maximum lunar libration of 6.8 degrees occurs at 23:00
12/12 The Moon is 0.4 degrees south of asteroid 4 Vesta, with an occultation taking place in most of South America and New Zealand, at 21:00
12/14 A minimum lunar libration of 6.4 degrees occurs at 12:00; the peak of the Geminid meteor shower (100 per hour) occurs at 17:00; Neptune is 0.7 degree north of the Moon, with an occultation taking place in part of Antarctica, the southern tip of South America, and South Africa, at 18:00
12/15 Mercury is at aphelion today
12/16 The Moon is 1.0 degree north of the asteroid 2 Pallas, with an occultation taking place in northwestern Canada, the eastern portion of Siberia, and Hawaii, at 1:00; Uranus is 2 degrees south of the Moon at 18:00
12/17 First Quarter Moon occurs at 10:18; Mercury is in superior conjunction with the Sun at 15:00
12/19 Mars is 88,165,000 kilometers from the Earth, its closest approach until the year 2016, at 0:00; a maximum lunar libration of 6.8 degrees occurs at 4:00
12/20 Saturn is stationary at 12:00
12/21 Pluto is in conjunction with the Sun at 0:00; the Moon is 1.0 degree north of the bright open cluster M45 (the Pleiades) in Taurus at 23:00
12/22 Venus is at its greatest heliocentric latitude north today; the winter solstice occurs at 6:08; the Moon is at perigee, subtending 33'07" from a distance of 360,815 kilometers, at 10:14
12/23 The peak of the Ursid meteor shower (10 per hour) occurs at 1:00; a minimum lunar libration of 6.5 degrees occurs at 1:00; Jupiter is in conjunction with the Sun at 6:00
12/24 The Full Moon (known as the Before Yule, Cold, Long Nights, and Oak Moon) occurs at 1:16; Mars is 0.9 degree south of the Moon, with an occultation taking place in northwestern Canada, Alaska, the Arctic, northern Russia, eastern Europe, and northeastern Great Britain, at 3:00; Mars (magnitude -1.6, apparent size 15.9") is at opposition at 20:00
12/26 The Moon is 0.4 degree north of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 12:00
12/27 A maximum lunar libration of 7.0 degrees occurs at 14:00
12/28 The Moon is 0.6 degree south of the first magnitude star Regulus (Alpha Leonis) at 5:00; Saturn is 3 degrees north of the Moon at 22:00
12/30 Comet 8P/Tuttle passes within a degree of the spiral galaxy M33 in Triangulum at 5:00
12/31 Last Quarter Moon occurs at 7:51

Although the eastern hemisphere will experience its peak, prospects for this year's Geminid meteor shower on the night of December 13 and morning of December 14 are quite good for observers in North America. The waxing crescent moon sets relatively early and won't pose a problem. Look for Earth-grazing meteors soon after dark. Activity should begin to increase appreciably after 10:00 p.m. EST, since the radiant is fairly high in the east by that time. By 2:00 a.m. EST, the radiant is nearly at the zenith and the hourly rate from a dark site may reach 100 per hour or more. Geminid meteors tend to be white in color, with a mix of faint meteors and bright fireballs. Unlike other meteor showers, the source of the Geminids is the asteroid 3200 Phaethon, which may actually be the remains of a no longer active comet.

The Moon occults the Pleiades before dusk on December 21, the longest night of the year. See http://www.lunar-occultations.com/io...21pleiades.htm for additional information on the occultation. A favorable libration on December 23 allows the summit of Mount Clementine, the most easily visible feature on the far-side of the Moon, to be seen for a total of four nights. The Moon is 21.0 days old and is located in Leo on December 1 at 0:00 UT. It attains its greatest northern declination (+28 degrees) for the month on December 23 and its greatest southern declination (-28 degrees) for the month on December 10. Times and dates for the lunar crater light rays predicted to occur this month are available at http://www.lunar-occultations.com/rlo/rays/rays.htm

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on December 1: Mercury (-0.8 magnitude, 4.9", 97% illuminated, 1.4 a.u., Libra), Venus (-4.2 magnitude, 17.8", 66% illuminated, 0.9 a.u., Virgo), Mars (-1.3 magnitude, 15.1", 97% illuminated, 0.6 a.u., Gemini), Jupiter (-1.8 magnitude, 31.8", 100% illuminated, 6.2 a.u., Ophiuchus), Saturn (0.7 magnitude, 18.1", 100% illuminated, 9.2 a.u., Leo), Uranus (5.9 magnitude, 3.5", 100% illuminated, 20.2 a.u., Aquarius), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.6 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 32.4 a.u., Sagittarius).

Visibility of the classical planets at mid-month for observers at 40 degrees north: Mars is in the evening sky in the east, in the southern sky at midnight, and in the west in the morning; Saturn is in the east at midnight and the southwest in the morning; and Venus in the southeast in the morning.

Since it reaches superior conjunction on December 17, Mercury is a difficult target this month.

Venus rises just prior to 4:00 a.m. on December 1. The first magnitude star Spica, Venus, and the Moon form a triangle in Virgo on the morning of December 5. Venus enters Libra on December 12. It lies between Alpha and Beta Librae on December 19. Venus shrinks in apparent size from 18 to 15" while its disk waxes in illumination from 66 to 76%.

Mars is very well placed for northern-hemisphere observers during December. It's positioned within 20 degrees of the zenith, as far north as it ever gets, every night for a minimum of two hours. Mars is less than half a degree north of the third magnitude star Epsilon Geminorum and shines with a brilliance of magnitude -1.4, as bright as Sirius, on the night of December 3. The Martian northern-hemisphere vernal equinox takes place on December 9. Due to its highly elliptical orbit, the Red Planet is closest to the Earth on December 18. Mars is less than three degrees north of the bright open cluster M35 in Gemini from December 21 to December 28. On the night of December 23, it's just 2.5 degrees north of M35. Mars reaches opposition on the night of December 24 and thus rises at sunset, transits the meridian at midnight, and sets at sunrise. On the night of opposition, Mars has a declination of 26 degrees and 46 arc minutes and at midnight is thus almost 77 degrees above the southern horizon. Since the Martian day, or sol, is 37.4 minutes longer than a terrestrial one, Martian surface features appear to move 9.11 degrees to the west each day. Mare Sirenum is visible at the beginning of the month at midnight, followed by Solis Lacus (the Eye of Mars) and Sinus Meridiani at mid-month, and Syrtis Major when the planet reaches opposition. Mars travels eleven degrees westward during December but retrogrades back into the constellation of Taurus on December 30. See the Mars Profiler at http://www.skyandtelescope.com/obser...avascript/mars for a hemispherical map of Martian surface features and http://www.skyandtelescope.com/obser...ons/index.html for the positions of the faint Martian moons Phobos and Deimos.

Jupiter enters Sagittarius on December 2. It slips out of view by the second week of the month as it heads toward conjunction on December 23.

Saturn rises shortly before midnight on December 1, at approximately 10:30 p.m. EST at mid-month, and at approximately 8:00 p.m. EST by month's end. It is at quadrature on December 1. Saturn's ring tilt angle is now only seven degrees. Titan (magnitude 8.5) is due north of the planet on December 4 and December 20. It is due south of Saturn on December 12 and December 28. Saturn's curious two-faced satellite Iapetus is due west of the planet by the listed separations on the following dates: December 2 (24"), December 8 (34"), December 14 (36"), December 20 (30"), December 26 (17"), and December 30 (6"). For further information on the five brightest satellites of Saturn, browse http://skytonight.com/observing/obje...t/3308506.html

Uranus is located just east of 81 and 82 Aquarii. By the end of December, the planet's eastward progress takes it to within two degees of the fourth magnitude star Phi Aquarii.

Neptune's retrograde motion increases throughout December. It's located about two degrees south of fourth magnitude Iota Capricorni.

Since Pluto is in conjunction with the Sun on December 18, it is not visible this month.

The coma of Comet 17P/Holmes continues to expand to monumental proportions as the comet travels through western Perseus. The historic comet will pass approximately 1.5 degrees to the northwest of the open cluster NGC 1245 on the night of December 2 and a bit more than 2 degrees to the west of the cluster on December 13.

Another periodic comet, Comet 8P/Tuttle, passes through Cassiopeia during December. It is near NGC 281 (the Pacman Nebula) on the night of December 22 but will be compromised by strong moonlight. The parent comet of the Ursid meteor shower passes close to M33 on the nights of December 29 and December 30. Comet 8P/Tuttle starts the month shining at ninth magnitude and may brighten to fifth magnitude at its peak.

This month the eighth magnitude asteroid 1 Ceres glides north-westward through the constellation of Cetus. It lies just to the south of the fourth magnitude star Mu Ceti.

One hundred and five binary and multiple stars for December: Gamma Andromedae, 59 Andromedae, Struve 245 (Andromeda); Struve 362, Struve 374, Struve 384, Struve 390, Struve 396, Struve 400, Struve 419, Otto Struve 67 (Camelopardalis); Struve 191, Struve Iota Cassiopeiae, Struve 263, Otto Struve 50, Struve 283, Struve 284 (Cassiopeia); 61 Ceti, Struve 218, Omicron Ceti, Struve 274, Nu Ceti, h3511, 84 Ceti, h3524, Lambda Ceti, Struve 330 (Cetus); h3527, h3533, Theta Eridani, Rho Eridani, Struve 341, h3548, h3565, Tau-4 Eridani, Struve 408, Struve 411, h3589, h3601, 30 Eridani, 32 Eridani (Eridanus); h3478, h3504, Omega Fornacis, Eta-2 Fornacis, Alpha Fornacis, See 25, Xi-3 Fornacis, h3596 (Fornax); Struve 268, Struve 270, h1123, Otto Struve 44, h2155, Nu Persei, Struve 297, Struve 301, Struve 304, Eta Persei, Struve 314, Otto Struve 48, Tau Persei, Struve 331, Struve 336, Es588, Struve 352, Struve 360, Struve 369, Struve 382, Struve 388, Struve 392, Struve 410, Struve 413, Struve 425, Otto Struve 59, Struve 426, 40 Persei, Struve 434, Struve 448, Es277, Zeta Persei, Struve 469, Epsilon Persei, Es878 (Perseus); Struve 399, Struve 406, Struve 401, Struve 422, Struve 430, Struve 427, Struve 435, 30 Tauri (Taurus); Epsilon Trianguli, Struve 219, Iota Trianguli, Struve 232, Struve 239, Struve 246, 10 Trianguli, Struve 269, h653, 15 Trianguli, Struve 285, Struve 286, Struve 310 (Triangulum)

Challenge binary star for December: 48 Cassiopeiae (Cassiopeia)

One hundred deep-sky objects for December: NGC 891 (Andromeda); IC 342, K6, St23, Tom 5 (Camelopardalis); Be65, IC 1848, K4, Mel15, NGC 896, NGC 1027, St2, Tr3 (Cassiopeia); M77, NGC 788, NGC 835, NGC 864, NGC 908, NGC 936, NGC 955, NGC 958, NGC 1015, NGC 1016, NGC 1022, NGC 1042, NGC 1052, NGC 1055, NGC 1087, NGC 1094 (Cetus); IC 2006, NGC 1084, NGC 1140, NGC 1187, NGC 1199, NGC 1209, NGC 1232, NGC 1291, NGC 1300, NGC 1309, NGC 1332, NGC 1337, NGC 1353, NGC 1357, NGC 1395, NGC 1400, NGC 1407, NGC 1421, NGC 1426, NGC 1440, NGC 1452, NGC 1453, NGC 1461 (Eridanus); NGC 1079, NGC 1097, NGC 1201, NGC 1292, NGC 1316 (Fornax I Galaxy Cluster), NGC 1317, NGC 1326, NGC 1344, NGC 1350, NGC 1360, NGC 1365, NGC 1371, NGC 1374, NGC 1379, NGC 1380, NGC 1381, NGC 1387, NGC 1398, NGC 1404, NGC 1406, NGC 1425 (Fornax); Bas10, Cz8, IC 351, IC 2003, K5, Mel 20, M34, NGC 869, NGC 884, NGC 957, NGC 1023, NGC 1058, NGC 1161, NGC 1245, NGC 1275 (Perseus I Galaxy Cluster), NGC 1333, NGC 1342, NGC 1444, Tr2 (Perseus); M45 (Taurus); NGC 777, NGC 784, NGC 890, NGC 925, NGC 949, NGC 959, NGC 978A/B (Triangulum)

Top ten binocular deep-sky objects for December: M34, M45, Mel15, Mel20, NGC 869, NGC 884, NGC 1027, NGC 1232, St2, St23

Top ten deep-sky objects for December: M34, M45, M77, NGC 869, NGC 884, NGC 891, NGC 1023, NGC 1232, NGC 1332, NGC 1360

Challenge deep-sky object for December: vdB14 (Camelopardalis)

The objects listed above are located between 2:00 and 4:00 hours of right ascension.

__________________
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