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/ August 2012 Celestial Calendar
August 2012 Celestial Calendar
July 31, 2012 2:20 PM
August Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
8/1 Mercury is at its greatest heliocentric latitude south today; a double Galilean satellite shadow transit begins at 0:42; a double Galilean satellite transit begins at 1:53
8/2 Venus is at its greatest heliocentric latitude south today; Full Moon (known as the Fruit, Grain, Green Corn, or Sturgeon Moon) occurs at 3:27
8/3 Jupiter is 5 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 4:00; the Moon is 6 degrees south of Neptune at 22:00
8/4 A double Galilean satellite shadow transit begins at 13:39; a double Galilean satellite transit begins at 15:16
8/6 A double Galilean satellite shadow transit begins at 8:08; Uranus is 5 degrees south of the Moon at 17:00
8/7 Mercury is stationary at 17:00
8/8 A double Galilean satellite shadow transit begins at 2:36; a double Galilean satellite transit begins at 4:38
8/9 Last Quarter Moon occurs at 18:55; asteroid 2 Pallas is stationary at 20:00
8/10 Venus is 5 degrees south of the bright open cluster M35 in Gemini at 2:00; the Moon is at apogee, subtending 30 arc minutes from a distance of 404,123 kilometers (247,679 miles), at 11:00
8/11 The Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to occur at 1:20; a double Galilean satellite shadow transit begins at 15:33; a double Galilean satellite transit begins at 18:03; Jupiter is 0.1 degree north of the Moon (with an occultation visible from Hawaii, the Marshall Islands, and most of Indonesia taking place) at 20:00
8/12 The peak of the Perseid meteor shower (a zenithal hourly rate of 60 to 100 per hour) occurs at 12:00
8/13 Mars is 1.9 degrees north of the first-magnitude star Spica (Alpha Virginis) at 0:00; a double Galilean satellite shadow transit begins at 10:48; Venus is 0.6 degree south of the Moon (with an occultation visible from most of North America, Japan, and eastern Asia taking place) at 20:00
8/15 A double Galilean satellite shadow transit begins at 4:44; a double Galilean satellite transit begins at 7:22
8/16 Mercury is 4 degrees north of the Moon at 5:00; Mercury is at greatest western elongation (19 degrees) at 12:00
8/17 Mars is 3 degrees south of Saturn at 8:00; New Moon (lunation 1109) occurs at 15:54
8/18 A double Galilean satellite shadow transit begins at 18:03; a double Galilean satellite transit begins at 20:43; Mercury is 2 degrees south of the bright open cluster M44 (Praesepe or the Beehive) in Cancer at 21:00
8/20 Mercury is at the ascending node today
8/21 Asteroid 10 Hygiea (magnitude 9.7) is at opposition at 20:00; the Moon is 1.0 degree south of Spica (with an occultation visible from New Zealand and most of Antarctica) at 22:00
8/22 Saturn is 5 degrees north of the Moon at 3:00; a double Galilean satellite shadow transit begins at 7:21; Mars is 2 degrees north of the Moon at 8:00
8/23 The Moon is at perigee, subtending 32 arc minutes from a distance of 369,728 kilometers (228,726 miles), at 19:00
8/24 First Quarter Moon occurs at 13:54; Neptune (magnitude 7.8, apparent size 2.3") is at opposition at 13:00; the Lunar X, also known as the Werner or Purbach Cross, an X-shaped clair-obscur illumination effect involving various ridges and crater rims located between the craters La Caille, Blanchinus, and Purbach, is predicted to occur at 9:31
8/25 Mercury is at perihelion today; a double Galilean satellite shadow transit begins at 20:40
8/29 A double Galilean satellite shadow transit begins at 9:58
8/31 Neptune is 6 degrees south of the Moon at 5:00; Full Moon, the second of the month, occurs at 13:58
John Flamsteed and Maria Mitchell were born this month. William Herschel discovered Enceladus on August 28, 1789. Asaph Hall discovered Deimos on August 11, 1877 and Phobos on August 17, 1877.
The peak of the Perseid meteor shower is slightly affected by moonlight this year. Comet 109P/Swift-Tuttle is the source of Perseid meteors. For more on this year’s Perseids, click on
The Moon is 0.8 days old and located in Sagittarius on August 1 at 0:00 UT. A second Full Moon, which is popularly known as a Blue Moon by one definition, occurs on August 31. The Moon is at its greatest northern declination on August 12 (+21.5 degrees) and its greatest southern declination on August 25 (-21.4 degrees). Longitudinal libration is at a maximum of +5.8 degrees on August 4 and +5.2 degrees on August 31 and a minimum of -5.0 degrees on August 16. Latitudinal libration is at a maximum of +6.6 degrees on August 18 and a minimum of -6.7 degrees on August 3 and -6.6 degrees on August 30. Visit
for tips on spotting extreme crescent Moons and
for Full Moon data. Times and dates for the lunar light rays predicted to occur in June 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 +4.6, 11.0", 2% illuminated, 0.61 a.u., Cancer), Venus (magnitude -4.6, 28.0", 42% illuminated, 0.60 a.u., Taurus), Mars (magnitude 1.1, 5.8", 90% illuminated, 1.63 a.u., Virgo), Jupiter (magnitude -2.2, 36.1", 99% illuminated, 5.47 a.u., Taurus), Saturn (magnitude 0.8, 16.7", 100% illuminated, 9.97 a.u., Virgo), Uranus (5.8 magnitude, 3.6", 100% illuminated, 19.53 a.u., Cetus), Neptune (7.8 magnitude, 2.4", 100% illuminated, 29.06 a.u., Aquarius), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.41 a.u., Sagittarius).
This month Mars and Saturn are visible in the southwest and Neptune in the east during the evening. At midnight, Uranus can be found in the east and Neptune in the southeast. In the morning, Mercury, Venus and Jupiter are in the east and Uranus and Neptune in the southwest.
At midmonth, Mercury can be seen during morning twilight, Venus rises at 3:00 a.m., Mars sets at 10:00 p.m., Jupiter rises at 1:00 a.m., and Saturn sets at 11:00 p.m. local time for observers at latitude 40 degrees north.
Notable celestial groupings take place on the morning of August 15 (the Moon, Mars, Saturn, and Spica) and on the evening of August 21 (the Moon, Mercury, Venus, Jupiter, and the bright stars of winter).
Mercury shines at magnitude 1.0 and should be visible in the eastern morning sky by August 11. On August 16, the speedy planet is at greatest eastern elongation and attains a brightness of magnitude -0.1. Mercury increases dramatically in magnitude and illuminated extent and decreases markedly in apparent size as the month progresses.
Venus lies two degrees south of the third-magnitude star Zeta Tauri on the morning of August 1. A daytime occultation of Venus by the waning crescent Moon takes place on the afternoon of August 13. Observers in western North America are favored. Only the disappearance can be seen from the East Coast. The occultation is discussed on page 51 of the August issue of Sky & Telescope. See
for a timetable for the event. Venus reaches greatest eastern elongation on August 15, one day earlier than Mercury. The brilliant planet rises 3.5 hours before the Sun that morning. Venus shines at magnitude -4.6 at the start of the month but fades to magnitude -4.2 by month’s end. During that time, it decreases 8 arc seconds in apparent size and increases 16% in illumination.
Mars moves eastward through Virgo this month. It passes between Saturn and Spica, which are separated by 4.5 degrees, on the evenings of August 13 and August 14. Mars (magnitude 1.1), Saturn (magnitude 0.8), and Spica (magnitude 1.0) fit into a circle with a diameter of less than five degrees, thus forming an astronomical trio, from August 8 through August 19. A waxing crescent Moon joins the trio on August 21. NASA’s Curiosity rover is scheduled to land on the Red Planet on August 5.
During August, Jupiter increases three arc seconds in apparent size. It’s situated five degrees from Aldebaran on August 1. Jupiter is occulted by the waning crescent Moon on August 11. Click on
to determine transit times of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at
Saturn is less than five degrees north of Spica this month. The planet shines a bit brighter than Spica and is a little more than 16 arc seconds in angular size during August. Its rings are inclined by 14 degrees. For further information on Saturn’s satellites, browse
Uranus can be found in northwestern Cetus, very close to the star 44 Piscium, which is exactly as bright (magnitude 5.8) as the planet. As August begins, Uranus is 1.6 degrees east-northeast of the star. By month’s end, the separation is just 0.85 degree.
Neptune is located 1.7 degrees east of the fifth-magnitude star 38 Aquarii on August 1. On August 31, the eighth planet is about half that distance from the star. When Neptune is at opposition on August 24, it is one degree to the east of 38 Aquarii, 11 degrees south of the celestial equator, and 29.0 astronomical units or four light-hours from the Earth.
Finder charts for Uranus and Neptune can be found at
Pluto is located in northern Sagittarius near the open cluster M25. The dwarf planet culminates during the mid-evening. Detailed finder charts are available on pages 52 and 53 of the June issue of Sky & Telescope and on page 236 of the RASC Observer’s Handbook 2012.
For more on the planets and how to locate them, see
No notable comets are expected to be visible this month. Comet C/2011 F1 (LINEAR) shines faintly at eleventh magnitude as it travels southeastward through the center of the constellation of Bootes. For additional information on comets visible in August, browse
Asteroids 1 Ceres and 4 Vesta shine at ninth and eighth magnitude respectively as they pass through Taurus during August, with Vesta positioned just north of Aldebaran on the morning of August 6. A finder chart appears on page 53 of the August issue of Sky & Telescope. Asteroid 18 Melpomene travels through southwestern Serpens Cauda. On August 11, the tenth-magnitude asteroid lies less than one degree to the west of the fourth-magnitude star Omicron Serpentis. Data on asteroid occultations taking place during August is available at
A free star map for August can be downloaded at
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)
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.
A man is a small thing, and the night is very large and full of wonders.
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