July 2011 Celestial Calendar & Observing Notes c/o Dave Mitsky

[Big Dipper]

July 2011 Celestial Calendar & Observing Notes courtesy of Dave Mitsky (calendar data also reproduced in our forum calendar).

All times, unless otherwise noted, are UT.

7/1 A partial solar eclipse that is visible only from the Antarctic Ocean, in an area south of Africa, reaches maximum at 8:38; New Moon (lunation 1095) occurs at 8:54

7/3 Mercury is 5 degrees north of the Moon at 2:00

7/4 Asteroid 21 Lutetia (magnitude 9.4) is at opposition at 7:00; the Earth is at aphelion (152,102,140 kilometers or 94,511,923 miles from the Sun) at 15:00

7/6 Venus is at the ascending node today; Mars is 5 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 6:00; Mercury is 0.3 degree south of the bright open cluster M44 (the Beehive or Praesepe) in Cancer at 21:00

7/7 The Moon is at perigee, subtending 32 arc minutes from a distance of 369,570 kilometers (229,640 miles), at 13:53

7/8 Mars is at the ascending node today; the Lunar X, also known as the Werner or Purbach Cross, an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to occur at 2:45; Saturn is 8 degrees north of the Moon at 4:00; First Quarter Moon occurs at 6:29

7/10 Uranus is stationary, with retrograde (western) motion to begin, at 8:00

7/15 Mercury is at the descending node today; Full Moon, known as the Hay or Thunder Moon, occurs at 6:40

7/18 Neptune is 6 degrees south of the Moon at 10:00

7/20 Mercury is at greatest eastern elongation (27 degrees) at 5:00

7/21 Uranus is 6 degrees south of the Moon at 7:00; the Moon is at apogee, subtending 29 arc minutes from a distance of 404,355 kilometers (251,254 miles), at 22:46

7/23 Last Quarter Moon occurs at 5:02

7/24 Jupiter is 5 degrees south of the Moon at 1:00; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 4:32

7/26 Mercury is at aphelion today

7/27 Asteroid 9 Metis (magnitude 9.6) is at opposition at 15:00; Mars is 0.5 degree north of the Moon, with an occultation occurring in Polynesia and most of the southern half of South America, at 17:00

7/28 The Moon is 1.8 degrees south of the bright open cluster M35 in Gemini at 5:00

7/29 Asteroid 2 Pallas (magnitude 9.5) is at opposition at 14:00; the Southern Delta Aquarid meteor shower (15 to 20 per hour) peaks at 15:00

7/30 New Moon (lunation 1096) occurs at 18:40

Friedrich Bessel was born this month.

The Southern Delta Aquarids occur during the dark-of-the-Moon period this year.

The Moon is 29.2 days old and is located in Gemini on July 1 at 0:00 UT. The so-called Lunar X occurs on the night of July 7. See page 41 of the July issue of Astronomy for more on this event. There are two Full Moons this month. A waning crescent Moon passes between the Pleiades and Hyades open star clusters on the morning of July 26. See IOTA Main Table of Contents for further information. The Moon is at its greatest northern declination of +23.3 degrees on July 27 and its greatest southern declination of –23.3 degrees on July 12. Longitudinal libration is at a maximum of +4.9 degrees on July 15 and a minimum of -5.9 degrees on July 28. Latitudinal libration is at a maximum of +6.8 degrees on July 6 and a minimum of -6.8 degrees on July 20. Visit http://www.astronomyblogs.com/member/saberscorpx/?xjMsgID=50821 for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur in June are available at Lunar Sunrise/Sunset Crater Rays

The Sun is located in Gemini on July 1. The Earth is farthest from the Sun on July 5, when it is 3.3% more distant than it was at perihelion. A partial solar eclipse, the first of the Saros series #156, takes place on July 1. This is the first new Saros series in 83 years. The eclipse reaches a maximum of 10% at 8:38 UT.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on July 1: Mercury (-0.5 magnitude, 5.8", 75% illuminated, 1.15 a.u., Cancer), Venus (-3.9 magnitude, 9.9", 98% illuminated, 1.68 a.u., Taurus), Mars (1.4 magnitude, 4.2", 97% illuminated, 2.22 a.u., Taurus), Jupiter (-2.2 magnitude, 37.1", 99% illuminated, 5.31 a.u., Aries), Saturn (0.9 magnitude, 17.4", 100% illuminated, 9.55 a.u., Virgo), Uranus (5.8 magnitude, 3.6", 100% illuminated, 19.98 a.u., Pisces), Neptune (7.8 magnitude, 2.3", 100% illuminated, 29.37 a.u., Aquarius), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.04 a.u., Sagittarius).

Mercury is located in the west and Saturn in the southwest during the evening. At midnight, Saturn is in the west, Uranus in the east, and Neptune in the southeast. In the morning, Venus can be found in northeast, Mars and Jupiter in the east, Uranus in the southeast, and Neptune in the south.

At midmonth, Mercury is visible during evening twilight, Mars rises at 3:00 a.m. EDT, Jupiter rises at 1:00 a.m., and Saturn sets at midnight for observers at latitude 40 degrees north.

Mercury reaches maximum eastern elongation on July 20, six days before aphelion. This apparition favors the southern hemisphere but the planet should be visible 30 minutes after sunset about eight degrees above the horizon. Mercury decreases in brightness by over a magnitude during the course of the month.

Venus disappears into the morning twilight in early July. It crosses the ecliptic plane on July 6.

A rather faint Mars passes north of the ecliptic on July 8. It lies between Beta and Zeta Tauri on the mornings of July 25 and July 26.

Jupiter increases in apparent size by almost 10% to 40.5 arc seconds and brightens by two-tenths of a magnitude during July. Click on Transit Times of Jupiter's Great Red Spot - Planets - SkyandTelescope.com to determine transit times of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at Jupiter's Moons Javascript Utility - Interactive Observing Tools - SkyandTelescope.com

Saturn reaches eastern quadrature on July 3. The gap between the Ringed Planet and the third-magnitude binary star Gamma Virginis (Porrima) widens as July progresses. The angle of inclination of Saturn’s rings increases to 8.0 degrees by month’s end. Eighth-magnitude Titan is at greatest eastern elongation on July 1 and July 17 and greatest western elongation on July 9 and July 25. Saturn’s odd moon Iapetus reaches greatest eastern elongation on July 20, at which time it lies eight arc minutes from the planet and shines dimly at twelfth-magnitude. For further information on Saturn’s satellites, browse Saturn's Moons Javascript Utility - Interactive Observing Tools - SkyandTelescope.com

Uranus is stationary on July 10 and then begins to retrograde, moving westward with respect to the fixed stars. This change in apparent motion is due to Uranus being overtaken by the faster-moving Earth.

During the second week of the month, Neptune passes 0.3 degree south of the fifth-magnitude star 38 Aquarii. The gas giant is "one year old" on July 12, completing its first orbit since its discovery by Johann Galle in 1846. At the time of its discovery, Neptune was less than two degrees from Saturn.

Finder charts for Uranus and Neptune are posted at How to Find Uranus and Neptune - Planets - SkyandTelescope.com

Pluto reached opposition late last month and is well-placed for observing during the middle of the night. It’s positioned 0.1 degree south of the ninth-magnitude star SAO 161442 during the first week of July. A finder chart is available on pages 64 and 65 of the July 2011 issue of Sky & Telescope.

For more on the planets and how to locate them, browse The Naked Eye Planets in the Night Sky (and how to identify them)

Comet C/2009 P1 (Garradd) passes through Aquarius and enters Pegasus this month. Browse http://cometchasing.skyhound.com and Visual Comets in the Future (Northern Hemisphere) for additional information on comets visible in July.

During July, asteroid 4 Vesta shines at sixth-magnitude as it travels southwestward through the constellation of Capricornus. The third largest of the asteroids is positioned a bit more than a degree to the northwest of the fifth-magnitude triple star Epsilon Capricorni during the first week of the month.

A free star map for July can be downloaded at Skymaps.com - Publication Quality Sky Maps & Star Charts

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 binocular deep-sky objects for July: IC 4665, LDN 1773, M4, M6, M7, M10, M12, M13, M92, NGC 6231

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)

The objects listed above are located between 16:00 and 18:00 hours of right ascension.

[Adz]

Thanks Andy exactly the information that will be helpful tonight.