April 2007 Calendar by Dave Mitsky

All times, unless otherwise noted, are UT (subtract 4 hours and, when appropriate, 1 calendar day for EDT)

4/1 Pluto is stationary at 0:00; Mercury is 1.6 degrees south of Uranus at 7:00; a minimum lunar libration of 2.4 degrees occurs at 15:00
4/2 Full Moon, known as the Egg or Grass Moon and the smallest one of 2007, occurs at 17:15
4/3 The Moon is at apogee, subtending 29'24" from a distance of 406,329 km, at 9:00; the Moon is 1.3 degrees south of the first magnitude star Spica (alpha Virginis) at 17:00
4/5 A double Galilean shadow transit (Europa's shadow is followed by Ganymede's) begins at 20:07
4/6 Jupiter is stationary at 2:00
4/7 The Moon is 0.6 degree south of the first magnitude star Antares (alpha Scorpii), with an occultation taking place in southern South America, western Antarctica, New Zealand, and eastern Australia, at 13:00
4/8 Jupiter is 6 degrees north of the Moon at 9:00
4/9 A maximum lunar libration of 9.6 degrees occurs at 16:00
4/10 Asteroid 3 Juno (magnitude 9.7) is at opposition; Last Quarter Moon occurs at 18:04
4/11 Venus is 3 degrees south of the bright open cluster M45 (the Pleiades) in Taurus
4/13 A double Galilean shadow transit (Europa's shadow is followed by Ganymede's) begins at 0:05
4/14 Mars is 0.5 degree south of the Moon, with an occultation taking place in southern and eastern Asia, India, and eastern Africa, at 2:00; Uranus is 1.0 degree south of the Moon, with an occultation taking place in northwestern Canada, Alaska, Japan, and eastern Siberia, at 20:00
4/15 Mercury is at its greatest heliocentric latitude south today
4/16 A minimum lunar libration of 3.5 degrees occurs at 7:00
4/17 The Moon is at perigee, the second closest of 2007, subtending 33'27" from a distance of 357,135 km, at 6:00; New Moon (lunation 1043) occurs at 11:36
4/18 Asteroid 4 Vesta is stationary today
4/19 Venus is at perihelion today; the Moon is 0.9 degree north of M45 at 16:00
4/20 Saturn is stationary at 1:00; Venus is 3 degrees south of the Moon at 8:00
4/21 Venus is 7 degrees north of the first magnitude star Aldebaran (alpha Tauri) at 12:00
4/22 A maximum lunar libration of 9.6 degrees occurs at 7:00; the peak of the Lyrid meteor shower (20/hour) occurs at 16:00
4/24 First Quarter Moon occurs at 6:36; the Moon is 1.7 degrees north of the bright open cluster M44 (the Beehive Cluster) in Cancer at 13:00
4/25 Saturn is 1.1 degrees south of the Moon, with an occultation taking place in northern Greenland, northwestern Canada, Alaska, and eastern Siberia, at 10:00
4/26 Mercury is 3.5 degrees south-southeast of the Moon at 6:00; the Moon is 1.0 degree north of the first magnitude star Regulus (alpha Leonis), with an occultation taking place in northwestern North America and the Arctic, at 10:00
4/28 Mars is 0.7 degree south of Uranus at 19:00
4/29 A minimum lunar libration of 3.1 degrees occurs at 7:00
4/30 The Moon is at apogee, subtending 29'25" from a distance of 406,209 km, at 11:00; the Moon is 1.3 degrees south of Spica at 23:00

The Moon is at its greatest southern declination of -29 degrees on April 8 and its greatest northern declination of +29 degrees on April 21. It is 12.9 days old at 0:00 UT on April 1. Times and dates for the lunar 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 April 1: Mercury (0.0 magnitude, 16.4", 67% illuminated, 1.1 a.u., Aquarius), Venus (-4.0 magnitude, 13.6", 79% illuminated, 1.2 a.u., Aries), Mars (1.1 magnitude, 4.9", 93% illuminated, 1.9 a.u., Capricornus), Jupiter (-2.3 magnitude, 40.3", 99% illuminated, 4.9 a.u., Ophiuchus), Saturn (0.2 magnitude, 19.4", 100% illuminated, 8.6 a.u., Leo), Uranus (5.9 magnitude, 3.4", 100% illuminated, 20.9 a.u., Aquarius), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.5 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.9 a.u., Sagittarius).

This month Mercury is not well placed for northern hemisphere observers.

Venus lies just a bit more than two degrees to the south of the Pleiades on the evening of April 11 and is less than a degree northwest of the northern section of the Hyades on April 18. It passes 1/3 degree north of the 4.4 magnitude star 37 Tauri on April 14. At sunset, Venus is nearly 40 degrees above the horizon for observers at our latitude of 40 degrees north.

Mars moves into Aquarius on April 2. It rises in east-southeast in the early morning. On April 28, Mars and Uranus are in close conjunction with the fourth magnitude star Phi Aquarii half-way between the two planets.

Jupiter begins to retrograde on April 6. It rises around 11:00 p.m. by the end of April. Click on http://skyandtelescope.com/observing...icle_107_1.asp to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://skytonight.com/observing/obje...t/3307071.html

At the middle of the month, Saturn culminates at approximately 8:00 p.m. EDT and sets in the west-northwest prior to 3:00 a.m. Titan (magnitude 8.6) passes north of the planet on the nights of April 9 and April 24 and south of Saturn on the night of April 16. During April, Rhea shines at a magnitude of 10.0, Tethys at 10.5, and Dione at 10.5. Iapetus shines at magnitude 10.1 when it’s at greatest western elongation on April 13. It is due west of Saturn by the listed separations on the following dates: April 2 (21"), April 6 (30"), April 10 (36"), April 16 (38"), April 20 (34"), April 24 (26"), and April 30 (11"). On the night of April 12, Iapetus is about 3 times farther west from Saturn than is Titan. For further information on Saturn’s satellites, browse http://skytonight.com/observing/obje...t/3308506.html

Uranus is a difficult morning sky target.

This month Neptune is lost in morning twilight.

Pluto is located in northwestern Sagittarius.

Comet 2P/Encke travels through Aries during most of April. The sixth magnitude period comet can be found low in the western sky during the first half of the month. After April 15, it heads sunwards rapidly.

Asteroid 11 Parthenope (magnitude 10.3) undergoes a series of stellar appulses during April as it passes northwestwards through Virgo. On the night of April 9, the asteroid briefly occults the ninth magnitude star HIP57258 for some observers.

Seventy-five binary and multiple stars for April: h4481 (Corvus); Aitken 1774, Gamma Crateris, Jacob 16, Struve 3072, h4456, Burnham 1078 (Crater); h4311, Burnham 219, N Hydrae, h4455, h4465 (Hydra); 31 Leonis, Alpha Leonis (Regulus), h2520, Struve 1417, 39 Leonis, Struve 1421, Gamma Leonis (Algieba), Otto Struve 216, 45 Leonis, Struve 1442, Struve 1447, 49 Leonis, Struve 1482, 54 Leonis, Struve 1506, Chi Leonis, 65 Leonis, Struve 1521, Struve 1527, Struve 1529, Iota Leonis, 81 Leonis, 83 Leonis, Tau Leonis, 88 Leonis, 90 Leonis, Struve 1565, Struve 1566, 93 Leonis, h1201, S Leonis (Leo); h2517, Struve 1405, Struve 1432, 33 Leo Minoris, Struve 1459, 40 Leo Minoris, Struve 1492 (Leo Minor); Struve 1401, Struve 1441, Struve 1456, Struve 1464, 35 Sextantis, 40 Sextantis, 41 Sextantis (Sextans); Struve 1402, Sturve 1415, Struve 1427, Struve 1462, Struve 1486, Struve 1495, Struve 1510, Struve 1520, Xi Ursae Majoris, Nu Ursae Majoris, Struve 1541, 57 Ursae Majoris, Struve 1544, Struve 1553, Struve 1561, Struve 1563, 65 Ursae Majoris, Otto Struve 241 (Ursa Major)

Challenge binary star for April: Gamma Sextantis

One hundred deep-sky objects for April: NGC 4024, NGC 4027 (Corvus); NGC 3511, NGC 3513, NGC 3672, NGC 3887, NGC 3892, NGC 3955, NGC 3962, NGC 3981 (Crater); NGC 3091, NGC 3109, NGC 3145, NGC 3203, NGC 3242, NGC 3309, NGC 3585, NGC 3621, NGC 3717, NGC 3904, NGC 3936 (Hydra); M65, M66, M95, M96, M105, NGC 3098, NGC 3162, NGC 3177, NGC 3185, NGC 3190, NGC 3226, NGC 3227, NGC 3300, NGC 3346, NGC 3367, NGC 3377, NGC 3384, NGC 3389, NGC 3412, NGC 3437, NGC 3489, NGC 3495, NGC 3507, NGC 3521, NGC 3593, NGC 3607, NGC 3608, NGC 3626, NGC 3628, NGC 3630, NGC 3640, NGC 3646, NGC 3655, NGC 3681, NGC 3684, NGC 3686, NGC 3691, NGC 3810, NGC 3842, NGC 3872, NGC 3900, NGC 4008 (Leo); NGC 3245, NGC 3254, NGC 3277, NGC 3294, NGC 3344, NGC 3414, NGC 3432, NGC 3486, NGC 3504 (Leo Minor); NGC 2990, NGC 3044, NGC 3055, NGC 3115, NGC 3156, NGC 3166, NGC 3169, NGC 3246, NGC 3423 (Sextans); IC 750, M97, M108, M109, NGC 3079, NGC 3184, NGC 3198, NGC 3310, NGC 3359, NGC 3610, NGC 3665, NGC 3675, NGC 3738, NGC 3877, NGC 3898, NGC 3941, NGC 3953, NGC 3998, NGC 4026 (Ursa Major)

Top 10 deep-sky objects for April: M65, M66, M95, M96, M97, M105, M108, M109, NGC 3115, NGC 3628

Challenge deep-sky object for April: Leo I (Leo)

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