July 2013 Celestial Calendar & Observing Notes c/o Dave Mitsky

[Big Dipper]

July 2013 Celestial Calendar & Observing Notes c/o Dave Mitsky

(calendar data also reproduced in our forum calendar).

*NB: Check out also the resources at the end of Dave's calendar for further reading/information*

All times unless otherwise noted are UT.

7/1 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 23:33

7/2 Pluto (magnitude 14.0, apparent size 0.1") is at opposition at 1:00

7/3 Venus lies within the boundaries of the bright open cluster M44 (the Beehive or Praesepe) in Cancer at 19:00

7/5 Venus is at its greatest heliocentric latitude north today; the Earth is at aphelion (152,097,427 kilometers or 94,508,959 miles from the Sun) at 15:00; Jupiter is 1.1 degrees south of the bright open cluster M35 in Gemini at 21:00

7/6 Mars is 4 degrees north of the Moon at 12:00

7/7 The Moon is at apogee, subtending 29'24" from a distance of 406,490 kilometers (252,581 miles), at 1:00

7/8 New Moon (lunation 1120) occurs at 7:14

7/9 Saturn is stationary at 4:00; Mercury is in inferior conjunction at 19:00

7/10 Venus is 7 degrees north of the Moon at 23:00

7/15 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 7:46

7/16 First Quarter Moon occurs at 3:18; the Moon is 0.3 degree north of the first-magnitude star Spica (Alpha Virginis), with an occultation occurring in the northwestern portion of South America, southern Central America, the Galapagos and Hawaiian Islands, and the northern Pacific Ocean, at 4:00; Mars is 0.4 degree south of M35 at 20:00

7/17 Saturn is 3 degrees north of the Moon at 1:00

7/18 Uranus is stationary, with retrograde (western) motion to begin, at 0:00

7/20 Asteroid 8 Flora (magnitude 8.7) is at opposition at 1:00; Mercury is stationary at 14:00

7/21 The Moon is at perigee, subtending 33'20" from a distance of 358,400 kilometers (222,702 miles), at 20:00

7/22 Venus is 1.2 degrees north of the first-magnitude star Regulus (Alpha Leonis) at 4:00; Mars is 0.8 degree north of Jupiter at 5:00; Full Moon, known as the Hay or Thunder Moon, occurs at 18:16

7/25 Neptune is 6 degrees south of the Moon at 6:00

7/27 Uranus is 3 degrees south of the Moon at 22:00

7/29 The Southern Delta Aquarid meteor shower (15 per hour) peaks at 3:00; Last Quarter Moon occurs at 17:43

7/30 Mercury is at greatest western elongation (20 degrees) at 9:00

7/31 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 10:33

Friedrich Bessel was born this month. The first photograph of a star, namely Vega, was taken on July 17, 1850. The first photograph of a total solar eclipse was taken on July 28, 1851.

Moonlight from the Last Quarter Moon will interfere with the peak of this year’s Southern Delta Aquarid meteor shower. Some other minor meteor showers with southern radiants taking place this month are the Alpha Capricornids, the Piscis Austrinids, and the Northern Delta Aquarids.

The Moon is 22.3 days old and is located in Pisces on July 1 at 0:00 UT. The Moon is at its greatest northern declination of +20.2 degrees on July 6 and its greatest southern declination of –20.1 degrees on July 20. Longitudinal libration is at a maximum of +7.7 degrees on July 27 and a minimum of -7.1 degrees on July 15. Latitudinal libration is at a maximum of +6.7 degrees on July 10 and a minimum of -6.6 degrees on July 23. Large tides will occur on July 22 through July 25. The waxing gibbous Moon occults the fourth-magnitude star Xi Ophiuchi for most of North America on the night of July 19-20 (page 49 of the July issue of Sky & Telescope). See http://www.lunar-occ...ota/iotandx.htm for information on other lunar occultations taking place this month. Visit http://saberdoesthes...does-the-stars/ for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur in June are available at http://www.lunar-occ...o/rays/rays.htm

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 and 1.7% farther than its average distance.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on July 1: Mercury (+3.2 magnitude, 11.5", 7% illuminated, 0.59 a.u., Gemini), Venus (-3.8 magnitude, 11.1", 90% illuminated, 1.50 a.u., Cancer), Mars (+1.5 magnitude, 3.8", 99% illuminated, 2.45 a.u., Taurus), Jupiter (-1.9 magnitude, 32.2", 100% illuminated, 6.13 a.u., Gemini), Saturn (+0.5 magnitude, 17.8", 100% illuminated, 9.36 a.u., Virgo), Uranus (+5.8 magnitude, 3.6", 100% illuminated, 19.83 a.u. on July 16, Pisces), Neptune (+7.8 magnitude, 2.3", 100% illuminated, 29.21 a.u. on July 16, Aquarius), and Pluto (+14.0 magnitude, 0.1", 100% illuminated, 31.49 a.u. on July 16, Sagittarius).

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

At midmonth, Mercury is visible during morning twilight, Venus sets at 10:00 p.m., Mars rises at 4:00 a.m., Jupiter rises at 4:00 a.m., and Saturn sets at 1:00 a.m. local daylight time for observers at latitude 40 degrees north.

Mercury is at inferior conjunction on July 9. It lies less than eight degrees below Mars on the morning of July 25. Mercury reaches greatest western elongation on July 30.

Positioned low in the west, Venus is not well-placed for northern hemisphere observers this month. The waxing crescent Moon lies seven degrees south of Venus on the evening of July 10. On July 12, the brilliant planet enters Leo. Venus (magnitude -3.9) passes 1.2 degrees north of Regulus (magnitude 1.4) on July 22. During July, Venus goes from 90 to 83% illuminated, while its angular size increases from 11 to 13 arc minutes.

A faint and tiny Mars lies four degrees north of a waning crescent Moon on July 6. The Red Planet departs Taurus and enters Gemini at mid-month, passing less than a degree south of the open cluster M35 on July 16 and July 17. At that time, Mars reaches its maximum northern declination (+23°58') for 2013.

Jupiter returns to the morning sky in early July. It passes less than one degree south of Mars on July 22. On that date, Jupiter’s disk is over eight times larger than that of Mars. Mercury, Mars, and Jupiter are all located in Gemini during the last week of July.

Saturn lies within one degree of the fourth-magnitude star Kappa Virginis this month. The planet’s rings span 39 arc minutes and are inclined by 17 degrees. Saturn is stationary in right ascension on July 9 and is at eastern quadrature on July 24. Eighth-magnitude Titan is north of the planet on July 1 and July 17 and south of it on July 9 and July 25. Saturn’s unusual moon Iapetus shines at twelfth-magnitude when it is positioned nine arc minutes east of Saturn on July 8 and shines at eleventh-magnitude on July 28 when it is two arc minutes south of the planet. For further information on Saturn’s satellites, browse http://www.skyandtel...pt/3308506.html

Uranus can be found four degrees south of the fourth-magnitude star Delta Piscium. The sixth planet is stationary on July 18 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.

Neptune is located 0.6 degree northwest of the fifth-magnitude star Sigma Aquarii this month. Neptune rises around midnight, about 90 minutes prior to Uranus.

Finder charts for Uranus and Neptune can be found at http://media.skyandt...eptune-2013.pdf

Pluto is well-placed for observing this month. It reaches opposition on July 1. The dwarf planet lies 2.8 degrees east of the open cluster M25 (magnitude 4.6) on July 4, about three arc minutes south of the globular cluster Palomar 8 (magnitude 10.9) on July 14, and about seven arc minutes north of the seventh-magnitude star SAO 187108 on July 31. Detailed finder charts are available on pages 52 and 53 of the June issue of Sky & Telescope and page 63 of the July issue of Astronomy. Online finder charts are posted at http://dcford.org.uk...luto_2013_2.pdf and http://britastro.org.../_Pluto2013.png

For more on the planets and how to locate them, browse http://www.nakedeyeplanets.com/

Comet C/2011 (PanSTARRS) glides southward through Draco for most of this month. The fading comet passes very close to the eleventh-magnitude spiral galaxy NGC 5678 on the night of July 17. Browse http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html for additional information on comets visible in July.

Asteroid 6 Hebe travels southward through Serpens this month. At month’s end, Hebe is positioned one degree west of the fourth-magnitude star Mu Serpentis. Asteroid 387 Aquitania shines at magnitude 9.7 when it reaches opposition in Aquila on July 12. Asteroid 8 Flora is located in Sagittarius and is a full magnitude brighter than Aquitania at opposition on July 20. The faint asteroid 1074 Beljawskya occults the ninth-magnitude star HIP 10921 in Aries on the morning of July 29. Data on this and other asteroid occultations taking place in July is available at http://www.asteroido.../2013_07_si.htm

A free star map for July can be downloaded at http://www.skymaps.com/downloads.html

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)

Notable variable star for July: R Ophiuchi

Notable carbon star for July: T Draconis

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.

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*Suggestions for further reading/information:*

Check out the following two sites (both are primarily UK-based) - each of which contain excellent celestial guides for the month ahead:

Astronomical Calendar

Astronomy.co.uk (site includes a short video highlighting some of the main celestial events for the month ahead).