Post by Dave Mitsky on Aug 2, 2016 19:50:51 GMT
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 The astronomical cross-quarter day known as Lammas or Lughnasadh occurs today; Venus is at its greatest latitude north of the ecliptic plane (3.4 degrees) at 13:00
8/2 Comet 9/P Tempel is at perihelion (1.54 astronomical units from the Sun) at 13:00; the Moon is 4.3 degrees south of the bright open cluster M44 in Cancer (approximately 3 degrees from the Sun) at 15:00; New Moon (lunation 1158) occurs at 20:45
8/4 Venus is 2.8 degrees north-northeast of the Moon at 5:00; the Moon is 1.6 degrees south-southwest of the first-magnitude star Regulus (Alpha Leonis) at 8:00; Mercury is 0.54 degree north of the Moon, with an occultation occurring in southernmost South America, various Pacific islands, and northern New Zealand, at 22:00
8/5 Mercury is at the descending node at 7:00; the Moon is at the ascending node at 7:49; Venus (magnitude -3.8) is 1.1 degrees north-northeast of Regulus (magnitude +1.4) at 9:00
8/6 Jupiter is 0.22 degree northeast of the Moon, with an occultation occurring in various Pacific islands, far northern Australia, Papua New Guinea, and the eastern portion of southeast Asia, at 3:00
8/8 The Moon is 5.5 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 16:00
8/9 Mars (magnitude -0.5) is in heliocentric conjunction with Pluto (magnitude +14.2) at 16:00
8/10 The Moon is at apogee, subtending 29' 34'' from a distance of 404,262 kilometers (251,197 miles), at 0:00; the Sun enters the constellation of Leo 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 10:55; First Quarter Moon occurs at 18:21
8/12 Mars is 8.0 degrees south of the Moon at 1:00; Saturn is 3.6 degrees south of the Moon at 13:00; the Moon is 9.8 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 13:00; the peak of the Perseid meteor shower (a zenithal hourly rate of 150 or more per hour) occurs at 13:00
8/13 Saturn is stationary in right ascension at 18:00
8/14 A double Galilean shadow transit (Ganymede’s shadow follows Io’s) begins at 7:32
8/15 Mercury is at aphelion (0.47 astronomical units from the Sun) at 16:00
8/16 Mercury is at greatest eastern elongation (27.4 degrees) at 21:00
8/18 Full Moon (known as the Fruit, Grain, Green Corn, or Sturgeon Moon) occurs at 9:27
8/19 Neptune is 1.0 degree south-southeast of the Moon, with an occultation occurring in northwest Canada, Alaska, and eastern Asia at 11:00; the Moon is at the descending node at 14:16
8/20 Mercury (magnitude +0.5) is 3.8 degrees southwest of Jupiter (magnitude -1.7) at 6:00; asteroid 2 Pallas (magnitude +9.2) is at opposition at 6:00
8/22 The Moon is at perigee, subtending nearly 32' 34'' from a distance of 367,050 kilometers (228,074 miles), at 1:00; Uranus is 2.9 degrees north-northwest of the Moon at 11:00
8/24 Mars (magnitude -0.4) is 1.8 degrees north of Antares (magnitude +1.0) at 15:00; Mars (magnitude -0.4) is 4.4 degrees south of Saturn (magnitude +0.5) at 16:00
8/25 Last Quarter Moon occurs at 3:41; the Moon is 0.22 degree north-northeast of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation occurring in northern Central America, Mexico, the southern United States, Hawaii, and Papua New Guinea, at 17:00
8/26 The Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to occur at 13:19
8/27 The Moon is 5.9 degrees south of the bright open cluster M35 in Gemini (62 degrees from the Sun) at 7:00; Venus (magnitude -3.8) is 0.07 degree north-northeast of Jupiter (magnitude -1.7), the closest appulse of two major planets in 2016, at 22:00
8/28 Mercury (magnitude +1.0) is 5.0 degrees south-southwest of Venus (magnitude -3.8) at 20:00
8/29 The Moon is 4.3 degrees south of M44 (29 degrees from the Sun) at 22:00
8/30 Mercury is stationary in right ascension at 1:00
8/31 The Moon is 1.6 degrees south-southwest of Regulus (approximately 9 degrees from the Sun) at 16:00
John Flamsteed and Maria Mitchell were born this month.
The gibbous phase of Mars was first observed by Francesco Fontana on August 24, 1638. William Herschel discovered Enceladus on August 28, 1789. Asaph Hall discovered Deimos on August 11, 1877 and Phobos on August 17, 1877.
Since the waxing gibbous Moon sets by approximately 1:00 a.m. local daylight time, the peak of the Perseid meteor shower on August 12th is not adversely affected by moonlight this year. Comet 109P/Swift-Tuttle is the source of Perseid meteors. The zenithal hourly rate may be exceptionally high this year, reaching a maximum of 150 or more meteors per hour, due to gravitational perturbations of the cometary debris stream by Jupiter. For more on this year’s Perseids, see pages 48-50 of the August issue of Sky & Telescope or click on www.timeanddate.com/astronomy/meteor-shower/perseid.html and earthsky.org/astronomy-essentials/everything-you-need-to-know-perseid-meteor-shower
The Moon is 27.6 days old, is illuminated 4.2%, subtends 31.6 arc minutes, and is located in Gemini on August 1st at 0:00 UT. The Moon is at its greatest northern declination on August 27th (+18.3 degrees) and its greatest southern declination on August 15th (-18.4 degrees). Longitudinal libration is at a maximum of +5.3 degrees on August 3rd and +5.5 degrees on August 30th and a minimum of -5.3 on August 16th. Latitudinal libration is at a maximum of +5.5 degrees on August 30th and a minimum of -6.8 degrees on August 13th. The Moon is at apogee on August 10th and perigee on August 22nd. New Moon (i.e., the dark of the Moon) occurs on August 2nd. The Moon passes 0.54 degree south of Mercury on August 4th, 2.8 degrees south-southwest of Venus on August 4th, 0.22 degree southwest of Jupiter on August 6th, 8.0 degrees north of Mars on August 12th, 3.6 degrees north of Saturn on August 12th, 1.0 degree north-northwest of Neptune on August 19th, and 2.9 degrees south-southeast of Uranus on August 22nd. The Moon occults Mercury on August 4th, Jupiter on August 6th, Neptune on August 19th, and Aldebaran on August 25th from certain parts of the world. Browse www.lunar-occultations.com/iota/bstar/bstar.htm for information on upcoming lunar occultations. Visit 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 August are available at www.lunar-occultations.com/rlo/rays/rays.htm
The Sun is located in Cancer on August 1st. It enters the constellation of Leo on August 10th.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on August 1: Mercury (magnitude -0.2, 5.9", 72% illuminated, 1.13 a.u., Leo), Venus (magnitude -3.8, 10.1", 96% illuminated, 1.65 a.u., Leo), Mars (magnitude -0.8, 13.0", 87% illuminated, 0.72 a.u., Libra), Jupiter (magnitude -1.7, 32.1", 100% illuminated, 6.15 a.u., Leo), Saturn (magnitude +0.3, 17.5", 100% illuminated, 9.48 a.u., Ophiuchus), Uranus (magnitude +5.8, 3.6", 100% illuminated, 19.44 a.u. on August 16th, Pisces), Neptune (magnitude +7.8, 2.4", 100% illuminated, 29.00 a.u. on August 16th, Aquarius), and Pluto (magnitude +14.2, 0.1", 100% illuminated, 32.36 a.u. on August 16th, Sagittarius).
This month Mercury, Venus, and Jupiter are visible in the west, Mars and Saturn in the south, and Neptune in the east during the evening. At midnight, Mars and Saturn can be found in the southwest, Uranus in the east, and Neptune in the southeast. In the morning, Uranus is in the south and Neptune is in the southwest.
At midmonth, Mercury is visible in evening twilight, Venus sets at 9:00 p.m. local daylight time, Mars sets at midnight, Jupiter sets at 9:00 p.m. local daylight time, and Saturn sets at 1:00 a.m. local daylight time for observers at latitude 40 degrees north.
Mercury undergoes its best apparition of 2016 for observers in the southern hemisphere this month. It is at the descending node on August 5th and is at greatest elongation east on August 16th. Mercury lies 3.8 degrees southwest of Jupiter on August 20th and 5.0 degrees south-southwest of Venus on August 28th. The speediest planet dims from magnitude -0.2 to magnitude +1.1 but increases in apparent size from 5.9 to 9.5 arc seconds this month.
On the afternoon of August 27th, Venus passes just 4.2 arc minutes north-northeast of Jupiter, the closest the two brightest planets have been since May of 2000. Mercury joins Venus and Jupiter in a triple conjunction on that date.
Mars shrinks from an apparent size of 13.0 arc seconds to 10.5 arc seconds during August and dims from magnitude -0.8 to magnitude -0.3. The Red Planet departs Libra and enters Scorpius in early August. Mars passes just to the south of the second-magnitude variable star Delta Scorpii on August 9th. It moves into Ophiuchus on August 21st but returns to Scorpius after August 27th. On August 24th, Mars passes 1.8 degrees north of Antares, creating a six degree line with Saturn to the north as it joins Saturn in conjunction.
Jupiter (magnitude -1.7), Mercury (magnitude -0.1), Regulus (magnitude +1.4), and Venus (magnitude -3.9) form a line almost 27 degrees long in the western sky after sunset on August 1st. Jupiter enters Virgo on August 9th. On August 28th, Mercury, Venus, and Jupiter fit within a 5.07-degree diameter circle. Jupiter is in conjunction with the Sun next month.
Saturn subtends 17 arc seconds in angular size this month. Its rings are inclined by 26 degrees and span 39 arc seconds. Over the course of the month, it decreases in brightness from magnitude +0.3 to magnitude +0.5. On August 13th, Saturn ends its retrograde motion. Eighth-magnitude Titan, Saturn’s largest satellite, is due north of the planet on August 8th and August 24th and due south on August 15th and August 31st. The peculiar satellite Iapetus shines at eleventh magnitude as it passes 2.1 arc minutes due south of Saturn on August 18th. It brightens to approximately tenth magnitude by August 31th when it is 7 arc minutes distant from Saturn. For additional information on Saturn’s satellites, browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Uranus is located 2.5 degrees north of the fifth-magnitude star Mu Piscium for the entire month. It rises prior to 11:00 p.m. local daylight time.
On August 1st, Neptune is situated 0.6 degree south of the fourth-magnitude star Lambda Aquarii. By the end of the month, the eighth planet lies 1.2 degrees southwest of that star.
Online finder charts for Uranus and Neptune can be found at www.nakedeyeplanets.com/uranus.htm and www.nakedeyeplanets.com/neptune.htm and also at www.skyandtelescope.com/wp-content/uploads/WEB_UrNep16_Finders.pdf
This month Pluto is situated not far to the southwest of the third-magnitude star Pi Sagittarii, which is part of the Sagittarius Teasthingy asterism. The dwarf planet is highest in altitude in the late evening. Articles on locating and observing Pluto are available on pages 48 and 49 of the July issue of Sky & Telescope and pages 64 and 65 of the July issue of Astronomy.
For more on the planets and how to locate them, see www.nakedeyeplanets.com/
Comet 9P/Tempel glows at eleventh magnitude as it heads southeastward through Virgo this month. The periodic comet is at perihelion on August 2nd and lies a bit more than one degree north of the sixth-magnitude star 86 Virginis on that date. For further information on comets visible this month, browse cometchasing.skyhound.com/ and www.aerith.net/comet/future-n.html
Asteroid 2 Pallas shines at ninth magnitude as it travels southwestward through western Pegasus. This main belt asteroid is located three degrees north-northwest of the second-magnitude star Enif (Epsilon Pegasi) on August 1st, and passes between Enif and the bright globular cluster M15 on August 10th. Pallas lies less than two degrees south of M15 on August 16th. The third most massive asteroid shines at magnitude +9.2 when it reaches opposition on August 20th. Other asteroids brighter than eleventh magnitude reaching opposition this month include 20 Massalia on August 1st, 19 Fortuna on August 10th, 349 Dembowska on August 11th, 85 Io on August 12th, 56 Melete on August 14th, 532 Herculina on August 23rd, and 17 Thetis on August 24th. For information on asteroid occultations taking place this month, see www.asteroidoccultation.com/2016_08_si.htm
A wealth of current information on solar system celestial bodies is posted at www.curtrenz.com/astronomy.html and nineplanets.org/
Free star maps for August can be downloaded at www.skymaps.com/downloads.html and www.telescope.com/content.jsp?pageName=Monthly-Star-Chart
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.
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
8/1 The astronomical cross-quarter day known as Lammas or Lughnasadh occurs today; Venus is at its greatest latitude north of the ecliptic plane (3.4 degrees) at 13:00
8/2 Comet 9/P Tempel is at perihelion (1.54 astronomical units from the Sun) at 13:00; the Moon is 4.3 degrees south of the bright open cluster M44 in Cancer (approximately 3 degrees from the Sun) at 15:00; New Moon (lunation 1158) occurs at 20:45
8/4 Venus is 2.8 degrees north-northeast of the Moon at 5:00; the Moon is 1.6 degrees south-southwest of the first-magnitude star Regulus (Alpha Leonis) at 8:00; Mercury is 0.54 degree north of the Moon, with an occultation occurring in southernmost South America, various Pacific islands, and northern New Zealand, at 22:00
8/5 Mercury is at the descending node at 7:00; the Moon is at the ascending node at 7:49; Venus (magnitude -3.8) is 1.1 degrees north-northeast of Regulus (magnitude +1.4) at 9:00
8/6 Jupiter is 0.22 degree northeast of the Moon, with an occultation occurring in various Pacific islands, far northern Australia, Papua New Guinea, and the eastern portion of southeast Asia, at 3:00
8/8 The Moon is 5.5 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 16:00
8/9 Mars (magnitude -0.5) is in heliocentric conjunction with Pluto (magnitude +14.2) at 16:00
8/10 The Moon is at apogee, subtending 29' 34'' from a distance of 404,262 kilometers (251,197 miles), at 0:00; the Sun enters the constellation of Leo 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 10:55; First Quarter Moon occurs at 18:21
8/12 Mars is 8.0 degrees south of the Moon at 1:00; Saturn is 3.6 degrees south of the Moon at 13:00; the Moon is 9.8 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 13:00; the peak of the Perseid meteor shower (a zenithal hourly rate of 150 or more per hour) occurs at 13:00
8/13 Saturn is stationary in right ascension at 18:00
8/14 A double Galilean shadow transit (Ganymede’s shadow follows Io’s) begins at 7:32
8/15 Mercury is at aphelion (0.47 astronomical units from the Sun) at 16:00
8/16 Mercury is at greatest eastern elongation (27.4 degrees) at 21:00
8/18 Full Moon (known as the Fruit, Grain, Green Corn, or Sturgeon Moon) occurs at 9:27
8/19 Neptune is 1.0 degree south-southeast of the Moon, with an occultation occurring in northwest Canada, Alaska, and eastern Asia at 11:00; the Moon is at the descending node at 14:16
8/20 Mercury (magnitude +0.5) is 3.8 degrees southwest of Jupiter (magnitude -1.7) at 6:00; asteroid 2 Pallas (magnitude +9.2) is at opposition at 6:00
8/22 The Moon is at perigee, subtending nearly 32' 34'' from a distance of 367,050 kilometers (228,074 miles), at 1:00; Uranus is 2.9 degrees north-northwest of the Moon at 11:00
8/24 Mars (magnitude -0.4) is 1.8 degrees north of Antares (magnitude +1.0) at 15:00; Mars (magnitude -0.4) is 4.4 degrees south of Saturn (magnitude +0.5) at 16:00
8/25 Last Quarter Moon occurs at 3:41; the Moon is 0.22 degree north-northeast of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation occurring in northern Central America, Mexico, the southern United States, Hawaii, and Papua New Guinea, at 17:00
8/26 The Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to occur at 13:19
8/27 The Moon is 5.9 degrees south of the bright open cluster M35 in Gemini (62 degrees from the Sun) at 7:00; Venus (magnitude -3.8) is 0.07 degree north-northeast of Jupiter (magnitude -1.7), the closest appulse of two major planets in 2016, at 22:00
8/28 Mercury (magnitude +1.0) is 5.0 degrees south-southwest of Venus (magnitude -3.8) at 20:00
8/29 The Moon is 4.3 degrees south of M44 (29 degrees from the Sun) at 22:00
8/30 Mercury is stationary in right ascension at 1:00
8/31 The Moon is 1.6 degrees south-southwest of Regulus (approximately 9 degrees from the Sun) at 16:00
John Flamsteed and Maria Mitchell were born this month.
The gibbous phase of Mars was first observed by Francesco Fontana on August 24, 1638. William Herschel discovered Enceladus on August 28, 1789. Asaph Hall discovered Deimos on August 11, 1877 and Phobos on August 17, 1877.
Since the waxing gibbous Moon sets by approximately 1:00 a.m. local daylight time, the peak of the Perseid meteor shower on August 12th is not adversely affected by moonlight this year. Comet 109P/Swift-Tuttle is the source of Perseid meteors. The zenithal hourly rate may be exceptionally high this year, reaching a maximum of 150 or more meteors per hour, due to gravitational perturbations of the cometary debris stream by Jupiter. For more on this year’s Perseids, see pages 48-50 of the August issue of Sky & Telescope or click on www.timeanddate.com/astronomy/meteor-shower/perseid.html and earthsky.org/astronomy-essentials/everything-you-need-to-know-perseid-meteor-shower
The Moon is 27.6 days old, is illuminated 4.2%, subtends 31.6 arc minutes, and is located in Gemini on August 1st at 0:00 UT. The Moon is at its greatest northern declination on August 27th (+18.3 degrees) and its greatest southern declination on August 15th (-18.4 degrees). Longitudinal libration is at a maximum of +5.3 degrees on August 3rd and +5.5 degrees on August 30th and a minimum of -5.3 on August 16th. Latitudinal libration is at a maximum of +5.5 degrees on August 30th and a minimum of -6.8 degrees on August 13th. The Moon is at apogee on August 10th and perigee on August 22nd. New Moon (i.e., the dark of the Moon) occurs on August 2nd. The Moon passes 0.54 degree south of Mercury on August 4th, 2.8 degrees south-southwest of Venus on August 4th, 0.22 degree southwest of Jupiter on August 6th, 8.0 degrees north of Mars on August 12th, 3.6 degrees north of Saturn on August 12th, 1.0 degree north-northwest of Neptune on August 19th, and 2.9 degrees south-southeast of Uranus on August 22nd. The Moon occults Mercury on August 4th, Jupiter on August 6th, Neptune on August 19th, and Aldebaran on August 25th from certain parts of the world. Browse www.lunar-occultations.com/iota/bstar/bstar.htm for information on upcoming lunar occultations. Visit 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 August are available at www.lunar-occultations.com/rlo/rays/rays.htm
The Sun is located in Cancer on August 1st. It enters the constellation of Leo on August 10th.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on August 1: Mercury (magnitude -0.2, 5.9", 72% illuminated, 1.13 a.u., Leo), Venus (magnitude -3.8, 10.1", 96% illuminated, 1.65 a.u., Leo), Mars (magnitude -0.8, 13.0", 87% illuminated, 0.72 a.u., Libra), Jupiter (magnitude -1.7, 32.1", 100% illuminated, 6.15 a.u., Leo), Saturn (magnitude +0.3, 17.5", 100% illuminated, 9.48 a.u., Ophiuchus), Uranus (magnitude +5.8, 3.6", 100% illuminated, 19.44 a.u. on August 16th, Pisces), Neptune (magnitude +7.8, 2.4", 100% illuminated, 29.00 a.u. on August 16th, Aquarius), and Pluto (magnitude +14.2, 0.1", 100% illuminated, 32.36 a.u. on August 16th, Sagittarius).
This month Mercury, Venus, and Jupiter are visible in the west, Mars and Saturn in the south, and Neptune in the east during the evening. At midnight, Mars and Saturn can be found in the southwest, Uranus in the east, and Neptune in the southeast. In the morning, Uranus is in the south and Neptune is in the southwest.
At midmonth, Mercury is visible in evening twilight, Venus sets at 9:00 p.m. local daylight time, Mars sets at midnight, Jupiter sets at 9:00 p.m. local daylight time, and Saturn sets at 1:00 a.m. local daylight time for observers at latitude 40 degrees north.
Mercury undergoes its best apparition of 2016 for observers in the southern hemisphere this month. It is at the descending node on August 5th and is at greatest elongation east on August 16th. Mercury lies 3.8 degrees southwest of Jupiter on August 20th and 5.0 degrees south-southwest of Venus on August 28th. The speediest planet dims from magnitude -0.2 to magnitude +1.1 but increases in apparent size from 5.9 to 9.5 arc seconds this month.
On the afternoon of August 27th, Venus passes just 4.2 arc minutes north-northeast of Jupiter, the closest the two brightest planets have been since May of 2000. Mercury joins Venus and Jupiter in a triple conjunction on that date.
Mars shrinks from an apparent size of 13.0 arc seconds to 10.5 arc seconds during August and dims from magnitude -0.8 to magnitude -0.3. The Red Planet departs Libra and enters Scorpius in early August. Mars passes just to the south of the second-magnitude variable star Delta Scorpii on August 9th. It moves into Ophiuchus on August 21st but returns to Scorpius after August 27th. On August 24th, Mars passes 1.8 degrees north of Antares, creating a six degree line with Saturn to the north as it joins Saturn in conjunction.
Jupiter (magnitude -1.7), Mercury (magnitude -0.1), Regulus (magnitude +1.4), and Venus (magnitude -3.9) form a line almost 27 degrees long in the western sky after sunset on August 1st. Jupiter enters Virgo on August 9th. On August 28th, Mercury, Venus, and Jupiter fit within a 5.07-degree diameter circle. Jupiter is in conjunction with the Sun next month.
Saturn subtends 17 arc seconds in angular size this month. Its rings are inclined by 26 degrees and span 39 arc seconds. Over the course of the month, it decreases in brightness from magnitude +0.3 to magnitude +0.5. On August 13th, Saturn ends its retrograde motion. Eighth-magnitude Titan, Saturn’s largest satellite, is due north of the planet on August 8th and August 24th and due south on August 15th and August 31st. The peculiar satellite Iapetus shines at eleventh magnitude as it passes 2.1 arc minutes due south of Saturn on August 18th. It brightens to approximately tenth magnitude by August 31th when it is 7 arc minutes distant from Saturn. For additional information on Saturn’s satellites, browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Uranus is located 2.5 degrees north of the fifth-magnitude star Mu Piscium for the entire month. It rises prior to 11:00 p.m. local daylight time.
On August 1st, Neptune is situated 0.6 degree south of the fourth-magnitude star Lambda Aquarii. By the end of the month, the eighth planet lies 1.2 degrees southwest of that star.
Online finder charts for Uranus and Neptune can be found at www.nakedeyeplanets.com/uranus.htm and www.nakedeyeplanets.com/neptune.htm and also at www.skyandtelescope.com/wp-content/uploads/WEB_UrNep16_Finders.pdf
This month Pluto is situated not far to the southwest of the third-magnitude star Pi Sagittarii, which is part of the Sagittarius Teasthingy asterism. The dwarf planet is highest in altitude in the late evening. Articles on locating and observing Pluto are available on pages 48 and 49 of the July issue of Sky & Telescope and pages 64 and 65 of the July issue of Astronomy.
For more on the planets and how to locate them, see www.nakedeyeplanets.com/
Comet 9P/Tempel glows at eleventh magnitude as it heads southeastward through Virgo this month. The periodic comet is at perihelion on August 2nd and lies a bit more than one degree north of the sixth-magnitude star 86 Virginis on that date. For further information on comets visible this month, browse cometchasing.skyhound.com/ and www.aerith.net/comet/future-n.html
Asteroid 2 Pallas shines at ninth magnitude as it travels southwestward through western Pegasus. This main belt asteroid is located three degrees north-northwest of the second-magnitude star Enif (Epsilon Pegasi) on August 1st, and passes between Enif and the bright globular cluster M15 on August 10th. Pallas lies less than two degrees south of M15 on August 16th. The third most massive asteroid shines at magnitude +9.2 when it reaches opposition on August 20th. Other asteroids brighter than eleventh magnitude reaching opposition this month include 20 Massalia on August 1st, 19 Fortuna on August 10th, 349 Dembowska on August 11th, 85 Io on August 12th, 56 Melete on August 14th, 532 Herculina on August 23rd, and 17 Thetis on August 24th. For information on asteroid occultations taking place this month, see www.asteroidoccultation.com/2016_08_si.htm
A wealth of current information on solar system celestial bodies is posted at www.curtrenz.com/astronomy.html and nineplanets.org/
Free star maps for August can be downloaded at www.skymaps.com/downloads.html and www.telescope.com/content.jsp?pageName=Monthly-Star-Chart
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.