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August 2013 Celestial Calendar c/o Dave Mitsky

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August 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.

8/3 The Moon is at apogee, subtending 29 arc minutes from a distance of 405,832 kilometers (252,172 miles), at 9:00; Jupiter is 4 degrees north of the Moon at 22:00

8/4 Asteroid 3 Juno (magnitude 9.0) is at opposition at 1:00; Mars is 5 degrees north of the Moon at 11:00

8/5 Mercury is 7 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 3:00; Mercury is 4 degrees north of the Moon at 9:00

8/6 Asteroid 4 Vesta is in conjunction with the Sun at 4:00; New Moon (lunation 1121) occurs at 21:51

8/7 Mercury is at the ascending node today

8/10 Venus is 5 degrees north of the Moon at 2:00

8/12 Mercury is at perihelion today; the Moon is 0.6 degree north of the first-magnitude star Spica (Alpha Virginis), with an occultation visible from central Asia, northern India, China, southern Japan, southeast Asia, the Philippines, and the Marshall Islands, at 9:00; the peak of the Perseid meteor shower (a zenithal hourly rate of 60 to 100 per hour) occurs at 18:00

8/13 Saturn is 3 degrees north of the Moon at 8:00; 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 18:44

8/14 First Quarter Moon occurs at 10:56

8/16 Asteroid 7 Iris (magnitude 7.9) is at opposition at 17:00

8/18 Asteroid 1 Ceres is in conjunction with the Sun at 1:00

8/19 The Moon is at perigee, subtending nearly 34 arc minutes from a distance of 362,264 kilometers (225,102 miles), at 1:00; Mars is 6 degrees south of Pollux at 11:00

8/21 Full Moon (known as the Fruit, Grain, Green Corn, or Sturgeon Moon) occurs at 1:45; Neptune is 6 degrees south of the Moon at 15:00

8/22 Mercury is at its greatest heliocentric latitude north today

8/24 Uranus is 3 degrees south of the Moon at 7:00; Mercury is in superior conjunction at 21:00

8/27 Neptune (magnitude 7.8, apparent size 2.3") is at opposition at 2:00;

8/28 Last Quarter Moon occurs at 9:35

8/29 The Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to occur at 21:52

8/30 Venus is at the descending node today

8/31 The Moon is at apogee, subtending 29 arc minutes from a distance of 404,881 kilometers (251,581 miles), at 0:00; Jupiter is 4 degrees north of the Moon at 17:00

John Flamsteed and Maria Mitchell were born this month. The gibbous phase of Mars was first observed by Francesco Fontana on August 24, 1738. 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 not adversely affected by moonlight this year. Comet 109P/Swift-Tuttle is the source of Perseid meteors. For more on this year’s Perseids, click on http://www.skyandtelescope.com/observing/highlights/185454662.html

The Moon is 23.7 days old and located in Taurus on August 1 at 0:00 UT. The Moon is at its greatest northern declination on August 2 (+20.1 degrees) and August 29 (+19.9 degrees) and its greatest southern declination on August 16 (-19.9 degrees). Longitudinal libration is at a maximum of +6.9 degrees on August 24 and -6.0 degrees on August 12. Latitudinal libration is at a maximum of +6.6 degrees on August 6 and a minimum of -6.5 degrees on August 19. The Moon occults Epsilon Tauri (Ain) on August 1, Alpha Virginis (Spica) on August 12, and Alpha Librae (Zubenelgenubi) on August 13. Browse http://www.curtrenz.com/occultations and http://www.lunar-occultations.com/iota/bstar/bstar.htm for further information on these events. Visit http://saberdoesthestars.wordpress.com/2011/07/05/saber-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-occultations.com/rlo/rays/rays.htm

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 -0.1, 7.3", 44% illuminated, 0.92 a.u., Gemini), Venus (magnitude -3.9, 12.5", 83% illuminated, 1.33 a.u., Leo), Mars (magnitude +1.6, 3.9", 98% illuminated, 2.40 a.u., Gemini), Jupiter (magnitude -1.9, 33.0", 100% illuminated, 5.98 a.u., Gemini), Saturn (magnitude +0.6, 16.9", 100% illuminated, 9.86 a.u., Virgo), Uranus (+5.8 magnitude, 3.6", 100% illuminated, 19.36 a.u. on August 16, Pisces), Neptune (+7.8 magnitude, 2.4", 100% illuminated, 28.99 a.u. on August 16, Aquarius), and Pluto (+14.0 magnitude, 0.1", 100% illuminated, 31.76 a.u. on August 16, Sagittarius).

This month Venus is visible in the west, Saturn 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, Mars, and Jupiter are in the east and Uranus and Neptune in the southwest.

At midmonth, Venus sets at 9:00 p.m., Mars rises at 4:00 a.m., Jupiter rises at 3:00 a.m., and Saturn sets at 11:00 p.m. local daylight time for observers at latitude 40 degrees north.

Mercury shines at a negative magnitude and is well-placed in the morning sky for northern hemisphere observers during the early part of the month. The speedy planet lies between the waning crescent Noon and the first-magnitude star Pollux on the morning of August 5. Mercury disappears into the glare of the Sun by mid-month and reaches superior conjunction on August 24.

The waxing crescent Moon passes five degrees south of Venus on the evening of August 9. Venus lies quite close to the point of the autumnal equinox (12 hours right ascension, 0 degrees declination) in mid-July. Venus increases in apparent size by over two arc seconds and decreases 9% in illumination this month.

Mars traverses Gemini and enters Cancer by the latter part of the month. On the morning of August 4, the waning crescent Moon passes five degrees south of the planet. Mars occults the seventh-magnitude star HIP 37579 on the morning of August 18 for observers in Alaska and the westernmost part of Canada. The Red Planet is close to Pollux at that time. By month’s end, Mars is 25 degrees above the eastern horizon less than an hour before sunrise for observers at latitude 40 degrees north.

Jupiter rises about 20 minutes prior to Mars at the start of the month. The two planets are located in Gemini and are separated by about 5 degrees at that time. Jupiter rises by 2:00 a.m. local daylight time on August 31. The waning crescent Moon and Jupiter are close companions on the mornings of August 3, August 4, and August 31. Click on http://www.skyandtelescope.com/observing/objects/planets/3304091.html?page=1&... to determine transit times of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://www.skyandtelescope.com/observing/objects/javascript/3307071.html

Saturn is a little more than 16 arc seconds in angular size during August. Its rings are inclined by 17 degrees and span 38 arc seconds at the start of the month. Eighth-magnitude Titan is north of the planet on August 2 and August 18 and south of it on August 10 and August 26. Saturn’s unusual moon Iapetus is at greatest western elongation on August 17. For further information on Saturn’s satellites, browse http://www.skyandtelescope.com/observing/objects/javascript/3308506.html

Uranus can be found 3.6 degrees south of the fourth-magnitude star Delta Piscium in southern Pisces.

Neptune is located 1.1 degrees west of the fifth-magnitude star Sigma Aquarii on August 1. By August 31, the eighth planet’s retrograde motion has placed it 1.8 degrees from the star. When Neptune is at opposition on August 27, the eighth planet is positioned 11 degrees south of the celestial equator and is 29.0 astronomical units or four light-hours from the Earth.

Finder charts for Uranus and Neptune can be found at http://media.skyandtelescope.com/documents/Uranus-Neptune-2013.pdf and on page 81 of the August issue of Astronomy.

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, on page 63 of the July issue of Astronomy, and on page 243 of the RASC Observer’s Handbook 2013. Online finder charts are posted at http://dcford.org.uk/findercharts/22pluto_2013_2.pdf and http://britastro.org/computing/ch/_Pluto2013.png

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

For information on comets visible in August, browse http://cometchasing.skyhound.com/ and http://www.aerith.net/comet/future-n.html

Asteroid 7 Iris travels south-westward through Aquarius this month. The eight-magnitude main belt asteroid is only 40 arc minutes north of the third-magnitude star Beta Aquarii when it reaches opposition on August 16. Asteroid 3 Juno shines at ninth magnitude when it reaches opposition in western Aquarius on the night of August 3. A finder chart can be found on page 51 of the August issue of Sky & Telescope. Data on asteroid occultations taking place this month is available at http://www.asteroidoccultation.com/2013_08_si.htm

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

Browse http://astrocast.tv/ for an informative video on astronomical events taking place this month.

SN 2013ej, a bright Type II supernova, is currently visible in the SA(s)c spiral galaxy M74 in Pisces. For further information, consult http://www.skyandtelescope.com/observing/home/Supernova-Erupts-in-Messier-74-... and http://www.rochesterastronomy.org/sn2013/sn2013ej.html

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.


*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).

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