August Calendar by Dave Mitsky

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

8/1 Today is Lammas, one of the cross-quarter days; the Moon is 0.4 degree south of the first magnitude star Spica (an occultation takes place in southern South America) at 1:00
8/2 Jupiter is 3.6 degrees north-northeast of the Moon at 8:00; First Quarter Moon occurs at 8:46; Jupiter reaches eastern quadrature at 12:00
8/3 A double Galilean shadow satellite transit (Europa's shadow is followed by Io's) takes place from 16:11 to 16:23; Venus is at the ascending node at 21:00
8/4 The Moon is 0.4 degree south of the first magnitude star Antares (an occultation takes place in southern South Africa and northeastern South America) at 18:00
8/5 Asteroid 6 Hebe (magnitude 7.8) reaches opposition at 0:00; a maximum lunar libration of 9.6 degrees occurs at 7:00
8/7 Mercury is at greatest western elongation (19.2 degrees) at 0:00; a double shadow transit (Europa's shadow is followed by Io's) takes place from 5:08 to 5:41; Saturn is in conjunction with the Sun at 11:00
8/8 Summer solstice occurs on Mars at 1:00
8/9 Full Moon, known as the Grain or Green Corn Moon, occurs at 10:54
8/10 The Moon is at perigee, subtending 33'13" from a distance of 359,750 km at 18:00; a double Galilean shadow satellite transit (Europa's shadow is followed by Io's) takes place from 18:05 to 19:01; the Sun enters Leo (ecliptic longitude 138.0 degrees) at 19:00; Mercury (magnitude -0.4) is 2.2 degrees southeast of Venus (magnitude -3.9) at 21:00
8/11 Neptune (magnitude 7.8, angular size 2.3") reaches opposition at 5:00; Uranus is 0.3 degree north of the Moon (an occultation takes place in western Africa and most of South America) at 6:00; a minimum lunar libration of 1.7 degrees occurs at 10:00
8/12 The Moon is at the ascending node (longitude 355.8 degrees) at 6:00; Asteroid 1 Ceres (magnitude 7.6) is at opposition at 15:00; the peak of the Perseid meteor shower (approximately 60/hour) occurs at 23:00
8/13 Mercury is at the ascending node at 6:00
8/14 A double Galilean shadow satellite transit (Europa's shadow is followed by Io's) takes place from 7:03 to 8:19
8/16 Mercury is 0.73 degree south-southwest of center of the bright open cluster M44 (the Beehive Cluster) at 1:00; Last Quarter Moon occurs at 1:51; the Moon is 0.69 degree north of the center of the bright open cluster M45 (the Pleiades) at 15:00
8/17 Mercury is at perihelion at 22:00
8/18 A maximum lunar libration of 9.6 degrees occurs at 3:00; Venus is 0.67 degree south of the center of M44 at 23:00
8/19 A double shadow transit (Ganymede's shadow is followed by Io's) takes place from 14:29 to 14:55
8/20 The Moon is 2.1 degrees south of the first magnitude star Pollux at 18:00
8/21 Mercury (magnitude -1.3) is 0.50 degree north-northeast of Saturn (magnitude 0.4) at 0:00; a double shadow transit (Europa's shadow is followed by Io's) takes place from 8:57 to 10:57; the Moon is 2.3 degrees north-northeast of M44 at 21:00
8/22 Neptune is 4 degrees north of the Moon at 13:00; Venus passes 1.2 degrees north of the first magnitude star Regulus at 15:00
8/23 Only one of the Galilean satellites, namely Callisto, will be visible from 3:14 to 4:23; the Moon is 1.8 degrees north-northeast of Regulus at 19:00; New Moon (lunation 1035) occurs at 19:10
8/24 Uranus is 2 degrees north of the Moon at 3:00; Asteroid 2 Pallas is stationary at 10:00; Europa, Io, and Ganymede form a tight group just after 13:30; a double shadow transit (Europa's shadow is followed by Io's) takes place from 21:55 to 0:03
8/25 Mars is 0.6 degree north of the Moon (an occultation takes place in the northeast and central regions of South America) at 14:00; a minimum lunar libration of 0.3 degree occurs at 18:00; the Moon is at the descending node (longitude 175.4 degrees) at 21:34
8/26 The Moon is at apogee, subtending 29'25" from a distance of 406,269 km, at 1:00; a double shadow transit (Io's shadow is followed by Ganymede's) takes place from to 17:05 to 18:31; Venus (magnitude -3.9) is 0.08 degree north-northeast of Saturn (magnitude 0.5) at 23:00
8/27 Mercury is 1.3 degrees north-northeast of Regulus at 19:00
8/28 Mercury is at its greatest latitude north of the ecliptic plane (7.0 degrees) at 4:00; the Moon is 0.6 degree southwest of Spica (an occultation takes place in southern New Zealand and Madagascar) at 8:00; a double shadow transit (Io's shadow is followed by Europa's) takes place from 11:02 to 13:00
8/29 Jupiter is 4.8 degrees north-northwest of the Moon at 22:00
8/31 First Quarter Moon, the second of the month, occurs at 22:57

A rising gibbous Moon compromises the Perseid meteor shower this year. Due to the bright moonlight, only about half of the usual hourly rate of Perseids may be visible.

On the morning of August 22, the thin crescent Moon, Mercury, Venus, and Saturn lie within a 7.5 degree diameter circle. 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

The planets on August 1: Mercury (1.2 magnitude, 9.0", 21% illuminated, Gemini), Venus (-3.7 magnitude, 10.9", 92% illuminated, Gemini), Mars (1.8 magnitude, 3.7", 98% illuminated, Leo), Jupiter (-2.1 magnitude, 37.3", 99% illuminated, Libra), Saturn (0.3 magnitude, 16.3", 100% illuminated, Cancer), Uranus (5.7 magnitude, 3.7", 100% illuminated, Aquarius), Neptune (7.8 magnitude, 2.3", 100% illuminated, Capricornus), and Pluto (13.9 magnitude, 0.1", 100% illuminated, Serpens Cauda).

Mercury is at greatest elongation from the Sun on August 7, when it appears 10 degrees above the eastern horizon a half hour before sunrise. For observers at 40 degrees north latitude, the speedy planet is at its highest altitude of approximately 16 degrees on the morning of August 9. Mercury is in quasi-conjunction with Venus on August 10, the last such event involving bright planets until 2010. A quasi-conjunction occurs when two planets pass within five degrees of each other without reaching the same ecliptic longitude or right ascension.

Venus rises less than two hours before the Sun and has close encounters with Mercury and Saturn this month. The second closest planetary appulse of 2006 occurs on August 26 when Venus and Saturn are less than a tenth of a degree apart.

By the end of August, Mars sets only 45 minutes after the Sun and is lost in its glare. The Red Planet is 5 degrees to the lower left of a young crescent Moon on the evening of August 25. Mars wanders from Leo into Virgo late in the month.

Jupiter moves three degrees closer to Zubenelgenubi (Alpha Librae) during the course of the month. The fifth planet is at eastern quadrature on August 2. This means that Jupiter is 90 degrees to the east of the Sun. As a result, eclipses of the Galilean satellites, with the exception of the non-eclipsing Callisto, will be more readily observable, since Jupiter's shadow extends farther to the east. Because Ganymede enters the shadow well to the east of the planetary disk, it provides the best eclipse views. There are an unusually high number of double shadow transits this month. (Few of them are visible from our location.) Red Spot Junior has passed by the Great Red Spot (GRS), apparently without incident. To determine the transit times of the GRS, click on http://skyandtelescope.com/observing...icle_107_1.asp

Saturn disappears from view early in the month but reappears in the morning sky by the third week of August. The Ringed Planet will be about one degree below Mercury on the morning of August 20. Saturn passes Mercury on August 21 and Venus on August 27.

During August, the seventh planet can be found to the east-northeast of the third magnitude star Lambda Aquarii. Uranus passes within 0.1 degree of the sixth magnitude star 81 Aquarii on August 6. The westward motion of Uranus places it 1.3 degrees east of Lambda Aquarii at month's end.

When Neptune reaches opposition on the night of August 10, it is situated 1.2 degrees to the north of Iota Capricornii (magnitude 4.3).

Pluto is positioned 0.5 degree southwest of Xi Serpentis (magnitude 3.5) on August 1. It's an additional 0.8 degree farther away from the star by the end of August.

The periodic comet 4P/Faye (period 7.5 years) glides northeastward through Pisces during August. The tenth magnitude comet is 15' south of the third magnitude star Eta Piscium on August 22. It passes just south of the tenth magnitude spiral galaxy M74 on the nights of August 26 and August 27.

The recently recovered periodic comet 177P/2006 M3 (Barnard 2) is visible through a binocular on August evenings as an eighth magnitude diffuse glow as it climbs through Hercules on its way to Draco. A finder chart is posted at http://www.skyhound.com/sh/comets/177P.gif

Asteroid 1 Ceres is at its brightest for the year as it travels westward through Piscis Austrinus. Two other bright asteroids, 6 Hebe and 15 Eunomia, also reach opposition this month. Asteroid 6 Hebe passes with 1 degree of the asterism M73 on the night of August 1. The seventh magnitude minor planet travels through Capricornus on a southwesterly course. During August, Asteroid 15 Eunomia passes through Capricornus and enters Sagittarius. On the night of August 8, the asteroid is very close to a field star of similar brightness. On August 29, 15 Eunomia (magnitude 8.4) reaches opposition.

Sixty binary and multiple stars for August: 5 Aquilae, Struve 2404, 11 Aquilae, Struve 2426, 15 Aquilae, Struve 2449, 23 Aquilae, Struve 2532, Pi Aquilae, 57 Aquilae (Aquila); Beta Cygni (Albireo), 16 Cygni, Delta Cygni, 17 Cygni (Cygnus); 41 & 40 Draconis, 39 Draconis, Struve 2348, Sigma Draconis, Struve 2573, Epsilon Draconis (Draco); 95 Herculis, 100 Herculis, Struve 2289, Struve 2411 (Hercules); Struve 2349, Struve 2372, Epsilon-1 & Epsilon-2 Lyrae (the Double-Double), Zeta-2 Lyrae, Beta Lyrae, Otto Struve 525, Struve 2470 & Struve 2474 (the Other Double-Double) (Lyra); 67 Ophiuchi, 69 Ophiuchi, 70 Ophiuchi, Struve 2276, 74 Ophiuchi (Ophiuchus); Mu Sagittarii, Eta Sagittarii, 21 Sagittarii, Zeta Sagittarii, H N 119, 52 Sagittarii, 54 Sagittarii (Sagittarius); Struve 2306, Delta Scuti, Struve 2373 (Scutum); Struve 2296, Struve 2303, 59 Serpentis, Theta Serpentis (Serpens Cauda); Struve 2445, Struve 2455, Struve 2457, 4 Vupeculae, Struve 2521, Struve 2523, Struve 2540, Struve 2586, Otto Struve 388, Struve 2599 (Vulpecula)

Challenge binary star for August: Alvan Clark 11 (ADS 11324) (Serpens Cauda)

Fifty-five deep-sky objects for August: B142, B143, NGC 6709, NGC 6738, NGC 6741, NGC 6751, NGC 6755, NGC 6781, NGC 6804 (Aquila); NGC 6819, NGC 6826, NGC 6834 (Cygnus); DoDz 9 (Hercules); M56, M57, NGC 6791 (Lyra); H20, M71 (Sagitta); B86, B87, B90, B92, B93, M8, M17, M18, M20, M21, M22, M23, M24, M25, M28, M54, M55, M69, M70, M75, NGC 6440, NGC 6445, NGC 6520, NGC 6818, NGC 6822 (Sagittarius); B110, B111, B113, Bas 1, M11, M26, NGC 6712 (Scutum); Cr 399, M27, NGC 6802, NGC 6940, St 1 (Vulpecula)

Challenge deep-sky object for August: Abell 53 (Aquila)

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