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

[Big Dipper]

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

All times, unless otherwise noted, are UT.

***Note: I will update the forum calendar later on today (as it's now gone 3am here)!***

8/1 Asteroid 1 Ceres is stationary at 0:00; Mercury is 1.5 degrees north of the Moon at 11:00

8/2 Mercury is stationary at 7:00; the Moon is at perigee, subtending 32'55" from a distance of 365,761 kilometers (225,532 miles), at 21:00

8/4 Saturn is 8 degrees north of the Moon at 12:00

8/5 Asteroid 4 Vesta (magnitude 5.6) is at opposition at 10:00

8/6 First Quarter Moon occurs at 11:08; 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 13:08; Mars is 0.5 degree south of the bright open cluster M35 in Gemini at 16:00

8/9 Venus is at perihelion today

8/13 The peak of the Perseid meteor shower (a zenithal hourly rate of 60 to 100 per hour) occurs at 6:00;

Full Moon (known as the Fruit, Grain, Green Corn, or Sturgeon Moon) occurs at 18:57

8/14 Neptune is 6 degrees south of the Moon at 16:00

8/15 Mercury is at its greatest heliocentric latitude south today

8/16 Venus is in superior conjunction at 13:00

8/17 Mercury is in inferior conjunction at 1:00; Uranus is 6 degrees south of the Moon at 13:00

8/18 The Moon is at apogee, subtending 29'46" from a distance of 405,161 kilometers (249,417 miles), at 16:00

8/20 Jupiter is 5 degrees south of the Moon at 12:00

8/21 Last Quarter Moon occurs at 21:54

8/22 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to occur at 15:46; Neptune (magnitude 7.8, apparent size 2.3") is at opposition at 23:00

8/24 The Moon is 1.9 degrees south of M35 at 15:00

8/25 Mars is 3 degrees north of the Moon at 14:00

8/26 Mercury is stationary at 4:00

8/28 Mercury is 3 degrees north of the Moon at 1:00

8/29 New Moon (lunation 1097) occurs at 3:04

8/30 Venus is at its greatest heliocentric latitude north today; Jupiter is stationary at 17:00; the Moon is at perigee, subtending 33'12" from a distance of 360,858 kilometers (226,380 miles), at 18:00

8/31 Saturn is 7 degrees north of the Moon at 23:00

John Flamsteed was born this month.

The peak of the Perseid meteor shower is severely compromised by a Full Moon this year. Only 20% of the meteors that would normally be seen will be visible, due to the bright moonlight.

The Moon is 0.8 days old and located in Leo on August 1 at 0:00 UT. The third-magnitude star Pi Sagittarii is occulted by the Moon on August 10 for observers in the eastern part of North America. See Watch a Star Wink Out on August 10th - Observing Blog - SkyandTelescope.com and Bright Star Occultation for additional information on this event. The Moon is at its greatest northern declination on August 23 (+23.2 degrees) and its greatest southern declination on August 8 (-23.3 degrees). Longitudinal libration is at a maximum of +5.4 degrees on August 10 and a minimum of -6.8 degrees on August 25. Latitudinal libration is at a maximum of +6.6 degrees on August 2 and +6.5 on August 30 and a minimum of -6.7 degrees on August 16. Visit http://www.astronomyblogs.com/member/saberscorpx/?xjMsgID=50821Lunar Sunrise/Sunset Crater Rays for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur this month are available at

The Sun is located in Cancer on August 1.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on August 1: Mercury (magnitude 1.2, 9.7", 24% illuminated, 0.69 a.u., Leo), Venus (magnitude -3.9, 9.7", 100% illuminated, 1.73 a.u., Cancer), Mars (magnitude 1.4, 4.4", 95% illuminated, 2.13 a.u., Taurus), Jupiter (magnitude -2.4, 40.6", 99% illuminated, 4.86 a.u., Aries), Saturn (magnitude 0.9, 16.5", 100% illuminated, 10.05 a.u., Virgo), Uranus (5.8 magnitude, 3.7", 100% illuminated, 19.50 a.u., Pisces), Neptune (7.8 magnitude, 2.4", 100% illuminated, 29.06 a.u., Aquarius), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.21 a.u., Sagittarius).

This month Saturn is visible in the west and Neptune in the southwest during the evening. At midnight, Jupiter can be found in the east and Uranus and Neptune in the southeast. In the morning, Mercury and Mars are in the east, Jupiter in the southeast, and Uranus and Neptune in the southwest.

At midmonth, Mars sets at 3:00 a.m. EDT, Jupiter rises at 11:00 p.m. EDT and transits the meridian at 6:00 a.m. EDT, and Saturn sets at 10:00 p.m. EDT for observers at latitude 40 degrees north.

Mercury disappears for the first part of the month as it approaches inferior conjunction on August 17. It reappears in the morning sky at the end of August.

Venus is not visible this month. It’s at superior conjunction on August 16.

Mars enters Gemini on August 4. It passes between the third-magnitude stars Eta and Mu Geminorum from August 8 to August 11 and 1.5 degrees south of the third-magnitude star Epsilon Geminorum on August 18 and August 19.

During August, Jupiter increases four arc seconds in apparent size and brightens by two-tenths of a magnitude. It reaches western quadrature on August 1. On the morning of August 3, Io disappears into Jupiter’s shadow at 3:19 a.m. EDT. Two hours later Ganymede is occulted by the planet. Jupiter begins retrograde (western) motion on August 30. 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’s rings are tilted approximately 9 degrees this month. The planet shines a bit brighter than Spica and is less than 16 arc seconds in angular size by the end of August.

Uranus rises about 90 minutes after Neptune.

Neptune is located 0.6 degree southwest of the fifth-magnitude star 38 Aquarii on August 1. On August 22, the eighth planet is 1.6 degrees north of the fourth-magnitude star Iota Aquarii. When Neptune is at opposition on August 22, it is four light hours from the Earth.

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

The dwarf planet Pluto is located in northern Sagittarius, due west of the open cluster M25 and due south of the emission nebula M17. It passes just south of the sixth-magnitude variable star Y Sagittarii during the second week of the month. 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)

On August 1, asteroid 1 Ceres shines at magnitude 8.4 and asteroid 4 Vesta at magnitude 5.6. Vesta, the brightest of the minor planets, can be seen with the naked-eye from a dark site this month. This will be the brightest apparition of an asteroid until 2018. When it reaches opposition on August 5, Vesta is close to a pair of stars in southern Capricornus. On August 31, Vesta passes 20 arc seconds to the south of the fourth-magnitude star Psi Capricorni on its southwestward course through the constellation. The Dawn spacecraft should reach its lowest orbit around Vesta in mid-August. Finder charts for Ceres and Vesta can be found on page 53 of the August 2011 issue of Sky & Telescope.

Comet C/2009 P1 (Garradd) heads westward from Pegasus into Sagitta this month. It’s positioned less than a degree north of the compact globular cluster M15 in western Pegasus on the first two nights of the month. On the night of August 26, the comet passes by the loose globular cluster M71. Browse Visual Comets in the Future (Northern Hemisphere) for additional information on these and other visible comets.

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

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)

Notable carbon star for August: V Aquilae

Eighty deep-sky objects for August: B139, B142, B143, NGC 6709, NGC 6738, NGC 6741, NGC 6751, NGC 6755, NGC 6772, NGC 6778, NGC 6781, NGC 6804, PK64+5.1 (Aquila); NGC 6819, NGC 6826, NGC 6834, (Cygnus); NGC 6643, NGC 6742 (Draco); DoDz 9 (Hercules); M56, M57, NGC 6703, NGC 6791, Ste1 (Lyra); NGC 6572, NGC 6633 (Ophiuchus); H20, M71 (Sagitta); B86, B87, B90, B92, B93, M8, M17, M18, M20, M21, M22, M23, M24, M25, M28, M54, M55, M69, M70, M75, NGC 6520, NGC 6544, NGC 6546, NGC 6553, NGC 6565, NGC 6603, NGC 6818, NGC 6822 (Sagittarius); IC 4703, IC 4756, M16, NGC 6604 (Serpens Cauda); B100, B101, B103, B104, B110, B111, B113, Bas 1, IC 1295, M11, M26, NGC 6649, NGC 6712 (Scutum); Cr 399 (asterism), M27, NGC 6802, NGC 6823, NGC 6834, NGC 6940, St 1 (Vulpecula)

Top ten binocular deep-sky objects for August: Cr 399, IC 4756, M8, M11, M17, M22, M24, M25, M27, NGC 6633 (IC 4756 and NGC 6633 are collectively known as the Binocular Double Cluster)

Top ten deep-sky objects for August: M8, M11, M16, M17, M20, M22, M24, M27, M55, M57

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

The objects listed above are located between 18:00 and 20:00 hours of right ascension.

[Irishnights]

Any chance the forum calendar URL could be pasted into your posts. I read the forum on my iPhone and it will make viewing the cal really easy then.

Keep up the excellent work. Thanks