July Calendar by Dave Mitsky

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

7/2 Venus is 0.8 degree south of Saturn at 1:00
7/3 Neptune is 1.3 degrees north of the Moon, with an occultation taking place near Antarctica, at 19:00
7/4 The Martian northern hemisphere winter begins today
7/5 Uranus is 1.9 degrees south of the Moon at 21:00
7/6 Venus is at the descending node today; asteroid 2 Pallas is stationary today; a minimum lunar libration of 3.6 degrees occurs at 0:00
7/7 Earth is at aphelion, 3.4% farther from the Sun (152,097,053 km) than at perihelion in January, at 0:00; Last Quarter Moon occurs at 16:54
7/9 Mars is 6.0 degrees south of the Moon at 15:00; the Moon is at perigee, subtending 32'25" from a distance of 368,528 km, at 22:20
7/10 Mercury is stationary at 2:00; the Moon is 1.0 degree north of the bright open cluster M45 (the Pleiades) in Taurus at 21:00
7/12 Mercury is at its greatest heliocentric latitude south at today; Venus is at its greatest brilliancy (magnitude -4.7) at 14:00
7/13 A maximum lunar libration of 7.3 degrees occurs at 0:00; Mercury is 9.0 degrees south of the Moon at 3:00
7/14 Asteroid 4 Vesta is stationary today; New Moon (lunation 1046) occurs at 12:04
7/15 The Moon is 1.1 degrees north of the bright open cluster M44 (the Beehive or Praesepe) in Cancer at 15:00
7/16 Venus is 2 degrees south of the first magnitude star Regulus (Alpha Leonis) at 15:00; Saturn is 0.04 degree north of the Moon, with an occultation taking place in western South America and Hawaii, at 23:00
7/17 The Moon is 0.3 degree north of Regulus, with an occultation taking place in northwestern Australia, the southern part of the Philippines, Indonesia, southern and western Asia, Europe, and Great Britain, at 9:00; Venus is 3 degrees south of the Moon at 10:00
7/19 A minimum lunar libration of 4.1 degrees occurs at 22:00
7/20 Mercury is its greatest western elongation of 20 degrees at 15:00
7/21 The Moon is 1.9 degrees south of the first magnitude star Spica (Alpha Virginis) at 21:00
7/22 First Quarter Moon occurs at 6:29; the Moon is at apogee, subtending 29'34" from a distance of 404,150 km, at 8:43
7/25 Venus is stationary at 13:00; the Moon is 0.6 degree south of the first magnitude star Antares (Alpha Scorpii), with an occultation taking place in southern Australia and New Zealand, most of Antarctica, and southern Africa, at 16:00; Jupiter is 6 degrees north of the Moon at 18:00
7/26 A maximum lunar libration of 7.9 degrees occurs at 16:00
7/28 The Southern Delta Aquarid meteor shower (approximately 20/hour) peaks at 13:00
7/30 The Full Moon, known as the Hay or Thunder Moon, occurs at 0:48
7/31 Mercury is at the ascending node today; Neptune is 1.3 degrees north of the Moon, with an occultation taking place in part of Antarctica, at 1:00

The Moon is 15.9 days old on July 1 at 0:00 UT. It’s at its greatest northern declination on July 12 (+28 degrees) and its greatest southern declination on July 26 (-28 degrees). 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 July 1: Mercury (5.3 magnitude, 11.8", 1% illuminated, 0.6 a.u., Gemini), Venus (-4.6 magnitude, 31.2", 36% illuminated, 0.5 a.u., Leo), Mars (0.7 magnitude, 6.3", 88% illuminated, 1.5 a.u., Aries), Jupiter (-2.5 magnitude, 45.0", 100% illuminated, 4.4 a.u., Ophiuchus), Saturn (0.6 magnitude, 16.7", 100% illuminated, 9.9 a.u., Leo), Uranus (5.8 magnitude, 3.6", 100% illuminated, 19.5 a.u., Aquarius), Neptune (7.8 magnitude, 2.3", 100% illuminated, 29.1 a.u., Capricornus), and Pluto (13.9 magnitude, 0.1", 100% illuminated, 30.4 a.u., Sagittarius).

Visibility of the classical planets at mid-month for observers at 40 degrees north: Venus and Saturn are located in the west and Jupiter in the south in the evening; Jupiter and Uranus are in the southeast at midnight; Mercury is in the east, Mars is in the southeast and Uranus in the southwest in the morning.

This month Mercury undergoes its best morning apparition of 2007 for observers in the northern hemisphere. From July 18 to July 28, it’s at least 10 degrees above the horizon in the east-northeast from our latitude of 40 degrees north. Mercury is 37 percent illuminated and shines at magnitude 0.3 when it is at greatest western elongation on July 20.

Venus and Saturn are in conjunction on the evening of July 1, when they will be separated by just 47 arc seconds. At that time, Venus (magnitude -4.6) is over 100 times brighter than Saturn (magnitude 0.6). Venus drops in altitude as it dives sunward after the middle of the month, the time of the planet’s greatest brilliance (magnitude -4.7). As it does so, it becomes an increasingly thin crescent, decreasing in illumination from 35 to 9 percent. At the same time, Venus grows noticeably in apparent size from 32 to 51 arc seconds. Venus sets only 40 minutes after the Sun by the end of July.

Mars rises just before 2:00 a.m. EDT at the beginning of the month and by 1:00 at month’s end. During that time, the Red Planet brightens from magnitude 0.7 to 0.5 but at 7 arc seconds is still too small for serious observation. On July 27, Mars passes from Aries into Taurus. It is located 7 degrees southwest of the bright open cluster M45 by July 31.

During July, Jupiter continues to shine brightly just 5 degrees to the north-northeast of Antares. On the night of July 25, the inner Galilean satellites Io and Europa are to the west of the planet, while the outer satellites Ganymede and Callisto are to the east of Jupiter at 10:30 p.m. EDT. Click on http://skyandtelescope.com/observing...icle_107_1.asp to determine transit times 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

Saturn rapidly drops away from Venus after their close conjunction on the night of July 1. By July 4, Saturn is almost 4 degrees to the lower right of Venus and by July 31 it is 6 degrees distant. On the night of July 16, a young crescent Moon lies between Saturn and Venus.

Uranus is positioned between Phi (magnitude 4.2) and 96 Aquarii (magnitude 5.6) in eastern Aquarius. It is 0.9 degree northeast of Phi on July 31.

Neptune is located approximately 2.3 degrees north of the fourth magnitude star Gamma Capricorni.

The dwarf planet Pluto is well placed in the southern sky on July evenings. It lies between the bright open cluster M23 and Xi Serpentis, about 8 degrees due west of the bright emission nebula M17 in Sagittarius. Finder charts for Uranus, Neptune, and Pluto can be found on page 60 of the July issue of Sky & Telescope.

Comet C/2006 VZ13 (LINEAR) travels through Draco and into Bootes during July. On the night of July 13, the tenth magnitude comet passes within one degree of the tenth magnitude lenticular galaxy M102. Nine nights later it is just 30 arc minutes away from the bright globular cluster M3.

Asteroid 4 Vesta dims from magnitude 6.1 to magnitude 6.7 this month. As July begins, it lies to the north of Graffias (Beta Scorpii). The asteroid heads southward towards Nu Scorpii as the month progresses.

Forty binary and multiple stars for July: Eta Draconis, 17 & 16 Draconis, Mu Draconis, Struve 2273, Nu-1 & Nu-2 Draconis, Psi Draconis (Draco); Kappa Herculis, Gamma Herculis, Struve 2063, 56 Herculis, Struve 2120, Alpha Herculis (Ras Algethi), Delta Herculis, Rho Herculis, Mu Herculis (Hercules); Rho Ophiuchi, Lambda Ophiuchi, 36 Ophiuchi, Omicron Ophiuchi, Burnham 126 (ADS 10405), Struve 2166, 53 Ophiuchi, 61 Ophiuchi (Ophiuchus); h5003 (Sagittarius); Xi Scorpii, Struve 1999, Beta Scorpii, Nu Scorpii, 12 Scorpii, Sigma Scorpii, Alpha Scorpii (Antares), h4926 (Scorpius); Struve 2007, 49 Serpentis, Struve 2031 (Serpens Caput); 53 Serpentis, Struve 2204, h4995, h2814 (Serpens Cauda); Epsilon Ursae Minoris (Ursa Minor)

Challenge binary star for July: 24 Ophiuchi

Sixty-five deep-sky objects for July: NGC 6140, NGC 6236, NGC 6340, NGC 6395, NGC 6412, NGC 6503, NGC 6543 (Draco); IC 4593, M13, M92, NGC 6106, NGC 6166, NGC 6173, NGC 6181, NGC 6207, NGC 6210, NGC 6229, NGC 6482 (Hercules); B61, B62, B63, B64, B72, IC 4634, IC 4665, LDN 42, LDN 1773, M9, M10, M12, M14, M19, M62, M107, NGC 6284, NGC 6287, NGC 6293, NGC 6304, NGC 6309, NGC 6356, NGC 6366, NGC 6369, NGC 6384, NGC 6401, Tr 26 (Ophiuchus); NGC 6440, NGC 6445 (Sagittarius); B50, B55, B56, Cr 316, M4, M6, M7, M80, NGC 6144, NGC 6153, NGC 6192, NGC 6231, NGC 6242, NGC 6302, NGC 6337, NGC 6451 (Scorpius); NGC 6217, NGC 6324 (Ursa Minor)

Top ten deep-sky objects for July: M4, M6, M7, M10, M12, M13, M92, NGC 6210, NGC 6231, NGC 6543

Challenge deep-sky object for July: NGC 6380 (Scorpius)

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