September Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
9/1 The equation of time, which yields the difference between mean solar time and apparent solar time, equals 0 at 20:00
9/2 Mars is in conjunction with the Sun (2.675 astronomical units from Earth, latitude 1.7 degrees) at 11:00; the Moon is 7.1 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 15:00
9/3 Mercury (magnitude -1.8) is 0.6 degree north-northeast of Mars (magnitude +1.7) at 17:00
9/4 Mercury is in superior conjunction with the Sun (1.369 AU from Earth, latitude 6.5 degrees) at 1:00
9/5 The Moon is 7.6 degrees north-northeast of the first-magnitude star Antares (Alpha Scorpii) at 23:00
9/6 Asteroid 135 Hertha (magnitude +9.6) is at opposition in Aquarius at 6:00; First Quarter Moon occurs at 3:10; the Moon is 2.3 degrees north-northeast of Jupiter 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 begin at 15:47
9/8 The Moon is 0.04 degree north of Saturn, with an occultation taking place in western Melanesia, western Micronesia, western and northern Australia, southern Indonesia, Madagascar, and eastern Africa, at 14:00; Jupiter is at eastern quadrature (90 degrees from the Sun) at 15:00; the Moon is at the descending node (longitude 286.0 degrees) at 18:00
9/9 The Moon is 0.1 degree north of Pluto, with an occultation taking place in northern South America, the Galapagos Islands, Easter Island, and Polynesia with the exception of Hawaii, at 3:00
9/10 Neptune (magnitude +7.8, apparent size 2.4") is at opposition at 8:00
9/13 The Moon is at apogee, subtending 29' 24" from a distance of 406,377 kilometers (252,511 miles), at 1:32; Mercury is (magnitude -0.9) 0.3 degree south-southwest of Venus (magnitude -3.9) at 14:00; the Moon is 3.4 degrees southeast of Neptune at 21:00
9/14 Full Moon (known as the Barley, Corn, or Fruit Moon), this year’s Harvest Moon, occurs at 4:33
9/17 The Sun enters Virgo, at longitude 174.2 degrees on the ecliptic, at 8:00; the Moon is 4.0 degrees south of Uranus at 20:00
9/18 Saturn is stationary in right ascension, with prograde (direct) motion to commence, at 5:00; Saturn is stationary in longitude, with prograde (direct) motion to commence, at 7:00
9/19 The Moon is 7.6 degrees southeast the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 23:00; Mars and Neptune are at heliocentric opposition (longitudes 167.4 degrees and 347.4 degrees) at 23:00
9/20 The Moon is 2.6 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 16:00
9/22 Last Quarter Moon occurs at 2:41; the Moon is 2.0 degrees south of the bright open cluster M35 in Gemini at 9:00; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to be visible at 16:28; Mercury is at the descending node through the ecliptic plane at 21:00
9/23 The Moon is at the ascending node (longitude 104.4 degrees) at 7:00; the Sun is at a longitude of 180 degrees at 7:50; the autumnal equinox occurs in the northern hemisphere at 7:50; the Moon is 9.5 degrees south of the first-magnitude star Castor (Alpha Geminorum) at 19:00
9/24 The Moon is 5.9 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 0:00; the Moon is 0.4 degree north of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 22:00
9/25 Asteroid 4 Vesta (magnitude +7.3) is stationary in Taurus at 5:00
9/26 The Moon is 3.2 degrees north-northeast of the first-magnitude star Regulus (Alpha Leonis) at 11:00
9/27 Saturn is at its southernmost declination (-22.5 degrees) at 21:00
9/28 The Moon is at perigee, subtending 33' 24" from a distance of 357,803 kilometers (222,328 miles), at 2:24; asteroid 21 Lutetia (magnitude +9.0) is at opposition in Capricornus at 4:00; New Moon (lunation 1197) occurs at 18:26
9/29 Mercury (magnitude -0.2) is 1.3 degree north-northeast of Spica at 9:00; the Moon is 4.0 degrees north-northeast of Venus at 16:00
9/30 The Moon is 7.0 degrees north-northeast of Spica at 1:00; the Moon is 5.8 degrees north-northeast of Mercury at 3:00
Nicolas Louis de Lacaille and Johann Gottfried Galle were born this month.
Jean-Dominique Maraldi discovered the globular cluster M15 on September 7, 1746. On September 11, 1746, Jean-Dominique Maraldi discovered the globular cluster M2. Nicolas-Louis de Lacaille discovered NGC 104 (47 Tucanae), the second largest and brightest globular cluster, on September 14th, 1751. William Herschel discovered the barred spiral galaxy NGC 7753 on September 12, 1784. William Herschel discovered the Saturnian satellite Mimas on September 17, 1789. Comet C/1793 S2 (Messier) was discovered by Charles Messier on September 27th, 1793. Karl Harding discovered asteroid 3 Juno on September 1, 1804. Neptune was discovered by Johann Gottfried Galle on September 23, 1846, using Urbain Le Verrier’s calculations of its position. On September 19, 1848, William Bond discovered Saturn’s fourteenth-magnitude satellite Hyperion, the first irregular moon to be discovered. On September 13, 1850, John Russell Hind discovered the asteroid 12 Victoria. E. E. Barnard discovered Jupiter’s fifth satellite, fourteenth-magnitude Amalthea, using the 36-inch refractor at the Lick Observatory, on September 9, 1892.
The minor meteor shower known as the Aurigids, which has a maximum hourly rate of just six per hour, peaks on the morning of September 1st. The peak of the minor meteor shower known as the Epsilon Perseids, with a maximum hourly rate of just five per hour, takes place on the evening of September 9th. The radiant is located near the second-magnitude star Algol (Beta Persei) at 03h15m, +40 degrees.
Information on passes of the ISS, the USAF’s X-37B, the HST, and other satellites can be found at http://www.heavens-above.com/
The Moon is 1.8 days old, subtends 33.3 arc minutes, is illuminated 3.8%, and is located in Virgo on September 1st at 0:00 UT. The Moon is at its greatest northern declination (+22.7 degrees) on September 23rd and its greatest southern declination (-22.5 degrees) on September 8th. Longitudinal libration is at a maximum of +7.9 degrees on September 5th and a minimum of -7.1 degrees on September 22nd. Latitudinal libration is at a maximum of +6.6 degrees on September 16th and a minimum of -6.6 degrees on September 2nd and -6.5 degrees on September 29th. The First Quarter Moon forms a noteworthy triangle with Antares and Jupiter on September 5th. The waxing gibbous Moon lies between Jupiter and Saturn on the following two nights. The waning gibbous Moon is located in the bright open cluster Melotte 25 (the Hyades) on the morning of September 20th. New Moon occurs on September 28th. Large tides will occur for several days thereafter. The Moon is at apogee (63.71 Earth-radii distant) on September 13th and at perigee (56.10 Earth-radii distant) on September 28th. The Moon occults Saturn on September 8th and Pluto on September 9th from certain parts of the world. The Moon occults the variable triple-star Propus (Eta Geminorum) for observers in the southwestern United States and Central America on the morning of September 22nd. For more on this event, see the article on page 50 of the September 2019 issue of Sky & Telescope. Browse http://www.lunar-occ...bstar/bstar.htm for information on this and other upcoming lunar occultations of bright stars. Visit http://saberdoesthes...s-the-stars/for tips on spotting extreme crescent Moons and http://www.curtrenz.com/moon06.html for Full Moon data. Click on https://www.calendar.../2019/september for a lunar phase calendar for this month. Times and dates for the lunar crater light rays predicted to occur in September are available at http://www.lunar-occ...o/rays/rays.htm
The zodiacal light, or the false dawn, is visible about two hours before sunrise from a dark site for two weeks beginning on September 26th. It can be seen in Leo, Cancer, Gemini, and Taurus. Articles on the zodiacal light appear at http://www.atoptics....ighsky/zod1.htm and http://oneminuteastr...zodiacal-light/
The Sun is located in Leo on September 1st. It enters Virgo on September 17th. The Sun crosses the celestial equator from north to south at 7:50 UT on September 23rd, the date of the autumnal equinox.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on September 1st: Mercury (magnitude -1.8, 5.0", 99% illuminated, 1.35 a.u., Leo), Venus (magnitude -3.9, 9.7", 100% illuminated, 1.72 a.u., Leo), Mars (magnitude +1.7, 3.5", 100% illuminated, 2.68 a.u., Leo), Jupiter (magnitude -2.2, 39.0", 99% illuminated, 5.06 a.u., Ophiuchus), Saturn (magnitude +0.3, 17.6", 100% illuminated, 9.42 a.u., Sagittarius), Uranus (magnitude +5.7, 3.7", 100% illuminated, 19.09 a.u. on September 16th, Aries), Neptune (magnitude +7.8, 2.4", 100% illuminated, 28.93 a.u. on September 16th, Aquarius), and Pluto (magnitude +14.3, 0.1", 100% illuminated, 33.40 a.u. on September 16th, Sagittarius).
This month Mercury and Venus are located in the west, Jupiter in the southwest, Saturn in the south, and Neptune in the east during the evening. At midnight, Saturn can be found in the southwest, Uranus in the east, and Neptune in the south. Uranus is in the southwest and Neptune is in the west in the morning sky.
Mercury is in superior conjunction on September 4th. It reappears in the evening sky as the month ends.
During September, Venus changes very little in apparent size and magnitude. After being lost in the glare of the Sun when it reached superior conjunction last month, Venus can be seen once again in the evening sky as September draws to a close.
Mars is in conjunction with the Sun on September 2nd, a week after reaching aphelion, and is about as far from the Earth as the Red Planet can get. Mars won’t be visible again until the third week of October.
Jupiter sets shortly after 10:00 p.m. DST by the end of September. It decreases in brightness to magnitude -2.0 and shrinks in angular diameter by 3.1 arc seconds this month. The First Quarter Moon passes two degrees north of Jupiter on September 6th. Jupiter is at eastern quadrature on September 8th. Transits by Io, starting at 8:04 p.m. EDT (0:04 UT September 5th), and its shadow, starting at 9:21 p.m. EDT (1:21 UT September 5th), take place on September 4th. A transit by Ganymede’s shadow occurs on September 5th, beginning at 11:22 p.m. EDT (3:22 UT September 6th). Ganymede passes 30 arc minutes due north of Callisto on the evening of September 19th. Information on Great Red Spot transit times and Galilean satellite events is available on pages 50 and 51 of the September 2019 issue of Sky & Telescope and online at http://www.skyandtel...watching-tools/ and https://www.projectp....com/jevent.htm
Saturn’s disk is 17 arc seconds in diameter at mid-month. At that time, its rings span 39 arc seconds and are tilted 25 degrees with respect to the Earth. Saturn fades from magnitude +0.3 to magnitude +0.5 this month. The Ringed Planet lies very close to the waxing gibbous Moon on September 8th, with an occultation occurring in some parts of the world. Saturn reaches its second stationary point on September 18th and then begins prograde or eastward motion. It is at its southernmost declination of -22.5 degrees on September 27th. Eighth-magnitude Titan, Saturn’s largest and brightest satellite, is due south of the planet on September 7th and due north of it on September 16th. Twelfth-magnitude Enceladus is located five arc seconds southwest of tenth-magnitude Tethys on September 4th. Saturn’s peculiar satellite Iapetus shines at eleventh magnitude on September 11th, when it is passes 1.4 arc minutes to the south of the planet. Iapetus brightens to tenth magnitude and is positioned 8.5 arc minutes from Saturn on September 30th. For further information on Saturn’s satellites, browse http://www.skyandtel...atching-tools/
Uranus is located in southwestern Aries, eleven degrees south of the second-magnitude star Hamal (Alpha Arietis). The planet lies 2.5 degrees south of the sixth-magnitude star 19 Arietis throughout the month. The waning gibbous Moon passes four degrees south of Uranus on September 17th. Visit http://www.bluewater...anus_2019_1.pdf and http://www.nakedeyep....com/uranus.htm for finder charts.
Neptune is located seven arc minutes east of the fourth-magnitude star Phi Aquarii on the first day of September. By September 5th, the ice giant planet lies just 42 arc seconds east of that star. As the day begins on September 6th, Neptune is a mere 13 arc seconds from Phi. Neptune subtends just 2.4 arc seconds, shines at magnitude +7.8, and lies at a distance of 4.0 light hours when it reaches opposition on September 10th. At that time, it is six arc minutes west of Phi Aquarii. As the month ends, Neptune is positioned 40 arc minutes from the star. The waxing gibbous Moon passes four degrees south of Neptune on September 13th. Browse http://www.bluewater...tune_2019_1.pdf and http://www.nakedeyep...com/neptune.htm for finder charts.
An article on Uranus and Neptune with finder charts appears on pages 48 and 49 of the September 2019 issue of Sky & Telescope. Finder charts for Uranus and Neptune are also available online at https://s22380.pcdn....020_updated.pdf
Pluto is located near the Teaspoon asterism in northeastern Sagittarius at a declination of nearly -22.5 degrees. Finder charts can be found at http://www.bluewater...9/Pluto2019.jpg and on page 48 and 49 of the July 2019 issue of Sky & Telescope and on page 243 of the RASC Observer’s Handbook 2019.
For more on the planets and how to locate them, see http://www.nakedeyeplanets.com/
During September, Comet C/2018 W2 (Africano) travels through Perseus, Andromeda, and Pegasus, and enters Pisces. It is at perihelion on September 5th and reaches a maximum brightness of approximately ninth magnitude on September 25th. On September 28th, the rapidly moving comet passes very close to the eleventh-magnitude galaxy NGC 7743 in southern Pegasus. Browse http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html for further information on comets visible this month. Other sources of information include https://theskylive.com/comets and http://www.shopplaza.nl/astro/ and http://britastro.org...arts_comet.html
Asteroid 1 Ceres heads southeastward between Ophiuchus and Scorpius during September. The dwarf planet shines at ninth magnitude as it passes 12 arc minutes north of the fifth-magnitude star Rho Ophiuchi on September 11th and 2.9 degrees north of the first-magnitude star Antares on September 15th. Asteroid 135 Hertha (magnitude +9.6) is at opposition in Aquarius on September 6th. Asteroid 21 Lutetia (magnitude +9.0) is at opposition in Capricornus on September 28th. Data on asteroid occultations taking place this month is available at http://www.asteroido.../2019_09_si.htm and http://www.poyntsour.../New/Global.htm
Various events taking place within our solar system are discussed at http://www.bluewater...ed-4/index.html
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in brightness from magnitude +2.1 to magnitude +3.4, on September 1st, 4th, 7th, 10th, 12th, 15th, 18th, 21st, 24th, 27th, and 30th. Consult page 49 of the September 2019 issue of Sky & Telescope for the minima times. On the morning of September 7th, Algol shines at minimum brightness (magnitude +3.4) for approximately two hours centered at 2:05 a.m. EDT (6:05 UT). It does the same at 10:54 p.m. EDT (2:54 UT September 10th) on the night of September 9th and 12:34 a.m. EDT (4:34 UT) on the morning of September 30th. For more on Algol, see http://stars.astro.i.../sow/Algol.html and http://www.solstatio...rs2/algol3.htm
Data on current supernovae can be found at http://www.rochester...y.org/snimages/
Information pertaining to observing some of the more prominent Messier galaxies can be found at http://www.cloudynig...ur-astronomers/
Author Phil Harrington offers an excellent freeware planetarium program for binocular observers known as TUBA (Touring the Universe through Binoculars Atlas), which also includes information on purchasing binoculars, at http://www.philharrington.net/tuba.htm
Eighty binary and multiple stars for September: 12 Aquarii, Struve 2809, Struve 2838 (Aquarius); Alpha Capricorni, Sigma Capricorni, Nu Capricorni, Beta Capricorni, Pi Capricorni, Rho Capricorni, Omicron Capricorni, h2973, h2975, Struve 2699, h2995, 24 Capricorni, Xi Capricorni, Epsilon Capricorni, 41 Capricorni, h3065 (Capricornus); Kappa Cephei, Struve 2751, Beta Cephei, Struve 2816, Struve 2819, Struve 2836, Otto Struve 451, Struve 2840, Struve 2873 (Cepheus); Otto Struve 394, 26 Cygni, h1470, h1471, Omicron Cygni, Struve 2657, 29 Cygni, 49 Cygni, 52 Cygni, 59 Cygni, 60 Cygni, 61 Cygni, Struve 2762 (Cygnus); Struve 2665, Struve 2673, Struve 2679, Kappa Delphini, Struve 2715, Struve 2718, Struve 2721, Struve 2722, Struve 2725 (in the same field as Gamma Delphini), Gamma Delphini, 13 Delphini, Struve 2730, 16 Delphini, Struve 2735, Struve 2736, Struve 2738 (Delphinus); 65 Draconis, Struve 2640 (Draco); Epsilon Equulei, Lambda Equulei, Struve 2765, Struve 2786, Struve 2793 (Equuleus); 1 Pegasi, Struve 2797, h1647, Struve 2804, Struve 3112, 3 Pegasi, 4 Pegasi, Kappa Pegasi, h947, Struve 2841, Struve 2848 (Pegasus); h1462, Struve 2653, Burnham 441, Struve 2655, Struve 2769 (Vulpecula)
Notable carbon star for September: LW Cygni
Fifty deep-sky objects for September: M2, M72, M73, NGC 7009 (Aquarius); M30, NGC 6903, NGC 6907 (Capricornus); B150, B169, B170, IC 1396, NGC 6939, NGC 6946, NGC 6951, NGC 7023, NGC 7160, NGC 7142 (Cepheus); B343, B361, Ba6, Be87, Cr 421, Do9, IC 4996, M29, M39, NGC 6866, NGC 6871, NGC 6888, NGC 6894, NGC 6910, NGC 6960, NGC 6992, NGC 6994, NGC 6995, NGC 7000, NGC 7008, NGC 7026, NGC 7027, NGC 7039, NGC 7048, NGC 7063, NGC 7086 (Cygnus); NGC 6891, NGC 6905, NGC 6934, NGC 7006 (Delphinus); NGC 7015 (Equuleus); M15 (Pegasus); NGC 6940 (Vulpecula)
Top ten binocular deep-sky objects for September: IC 1396, LDN 906, M2, M15, M29, M30, M39, NGC 6939, NGC 6871, NGC 7000
Top ten deep-sky objects for September: IC 1396, M2, M15, M30, NGC 6888, NGC 6946, NGC 6960, NGC 6992, NGC 7000, NGC 7009
Challenge deep-sky object for September: Abell 78 (Cygnus)
The objects listed above are located between 20:00 and 22:00 hours of right ascension.