October Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
10/1 Mercury is at greatest eastern elongation (25.8 degrees) at 16:00; Full Moon, known as the Blood or Sanguine Moon, and this year's Harvest Moon, occurs at 21:05
10/3 Venus is 0.09 degrees south of the first-magnitude star Regulus (Alpha Leonis) at 0:00; the Moon is 0.7 degrees south of Mars, with an occultation taking place in southwestern Africa, Ascension Island, most of western Antarctica, and southern and southeastern South America, at 3:00; the Moon is at apogee, subtending 29' 25" from a distance of 406,321 kilometers (252,476 miles), at 17:22
10/4 Pluto is stationary, with prograde or direct (eastward) motion to resume, at 16:00; the Moon is 3 degrees south of Uranus at 9:00
10/6 The Moon is 5.9 degrees southeast of the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 6:00; Mars is at its closest approach to the Earth (62,069,570 kilometers or 38,568,243 miles) at 14:00
10/7 The Moon is 4.4 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 0:00
10/8 The peak of the Draconid meteor shower (a zenithal hourly rate of 15 per hour) is predicted to occur at 3:00; the Moon is 0.02 degrees south of the bright open cluster M35 in Gemini at 20:00
10/9 Mercury is at its southernmost latitude from the ecliptic plane (-7.0 degrees) at 9:00
10/10 Last Quarter Moon occurs at 0:40; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to be visible at 12:59
10/11 Jupiter is at eastern quadrature (90 degrees from the Sun) at 14:00; the Moon is 2.4 degrees north-northeast of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 15:00
10/13 The Moon is 4.3 degrees north-northeast of Regulus at 6:00; Mars is at opposition (magnitude -2.6, angular size 22.4") at 23:00
10/14 The Moon is 4 degrees north of Venus at 0:00; Mercury is stationary, with retrograde motion to begin, at 4:00
10/15 Pluto is at its southernmost declination (-22.65 degrees) at 14:00
10/16 New Moon occurs (lunation 1210) occurs at 19:31; the Moon is 6.3 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 21:00; the Moon is at perigee, subtending 33' 29" from a distance of 356,912 kilometers (221,775 miles), at 23:46
10/17 The Moon is 7 degrees north of Mercury at 19:00; a double Galilean shadow transit (Io's shadow follows Callisto's) begins at 21:26
10/18 Saturn is at eastern quadrature (90 degrees from the Sun) at 14:00
10/19 The Moon is 5.6 degrees north-northeast of the first-magnitude star Antares (Alpha Scorpii) at 23:00
10/20 The Moon is at the descending node (longitude 261.3 degrees) at 16:00
10/21 The peak of the Orionid meteor shower (a zenithal hourly rate of 20 per hour) is predicted to occur at 6:00
10/22 The Moon is 2 degrees south of Jupiter at 17:00; the Sun's longitude is 210 degrees at 23:00
10/23 The Moon, Jupiter, and Saturn lie within a circle with a diameter of 6 degrees at 2:00; the dwarf planet/asteroid 1 Ceres is stationary at 3:00; the Moon is 3.0 degrees south of Saturn at 4:00; First Quarter Moon occurs at 13:23; asteroid 11 Parthenope (magnitude +9.4) is at opposition in Pisces at 14:00
10/24 The Lunar X, also known as the Purbach or Werner Cross, an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to be fully formed at 1:44
10/25 Mercury is in inferior conjunction with the Sun (0.671 astronomical units from the Earth, latitude -1.9 degrees) at 18:00
10/26 Asteroid 471 Papagena (magnitude +9.5) is at opposition in Cetus at 6:00
10/27 The Moon is 4 degrees south of Neptune at 6:00
10/28 Mercury is at the ascending node through the ecliptic plane at 11:00
10/29 The Moon is 2.7 degrees southeast of Mars at 19:00
10/30 The Moon is at apogee, subtending 29' 24" from a distance of 406,394 kilometers (252,522 miles), at 18:45; the Sun enters the constellation of Libra, at longitude 217.8 degrees on the ecliptic at 19:00; Venus is at perihelion (0.7184 astronomical units from the Sun) at 23:00
10/31 The Moon is 3 degrees south of Uranus at 13:00; Full Moon, the smallest of the year, occurs at 14:50; Uranus is at opposition (magnitude +5.7, angular size 3.7") at 16:00
Ejnar Hertzsprung and Henry Norris Russell were born this month.
The first recorded solar eclipse took place on October 22, 2136 BCE. Supernova SN 1604 (Kepler’s Supernova) became visible to the naked-eye on October 9, 1604. Giovanni Cassini discovered Saturn’s odd satellite Iapetus on October 25, 1671. M51a (the Whirlpool Galaxy) was discovered by Charles Messier on October 13, 1773. William Lassell discovered Triton, Neptune’s brightest satellite, on October 10, 1846. Maria Mitchell discovered Comet C/1847 T1 (Miss Mitchell’s Comet) on October 1, 1847. Asteroid 8 Flora was discovered by John Russell Hind on October 18, 1847. Two of the satellites of Uranus, Ariel and Umbriel, were discovered by William Lassell on October 24, 1851. Edwin Hubble discovered Cepheid variable stars in M31 (the Andromeda Galaxy) on October 5, 1923. Charles Kowal discovered 2060 Chiron, the first Centaur asteroid, on October 18, 1977. Michel Mayor and Didier Queloz announced the discovery of the exoplanet 51 Pegasi b (Dimidium) on October 6, 1995.
The Draconid (formerly the Giacobinid) meteor shower peaks on the night of October 7th/8th. The Draconids are quite variable and have produced meteor storms in 1933 and 1946. There is the possibility of higher than normal rates between 8:30 p.m. and 9:00 p.m. EDT (0:30 to 1:00 UT on October 8th) this year. The waxing gibbous Moon will rise around 9:00 p.m. EDT (1:00 UT on October 8th). Comet 21P/Giacobini-Zimmer is the parent comet of the Draconids. Consult https://earthsky.org/?p=3669 and https://skyandtelesc...howers-in-2020/ for additional information on the Draconid meteor shower. The Orionid meteor shower peaks on the night of October 21st/22nd and is not adversely affected by a waxing crescent Moon. Orionid meteors are fragments of Comet 1P/Halley. Browse https://www.timeandd...er/orionid.html and https://earthsky.org...d-meteor-shower or consult page 52 of the October 2020 issue of Sky & Telescope for more on the Orionids.
Information on Iridium flares and passes of the ISS, the USAF’s X-37B, the HST, Starlink, and other satellites can be found at www.heavens-above.com/
The zodiacal light may be visible in the pre-dawn eastern sky from a dark site for most of the second half of the month. Articles on the zodiacal light appear at https://www.atoptics...ighsky/zod1.htm and https://earthsky.org...t-or-false-dawn
The Moon is 13.4 days old, subtends 29.8 arc minutes, is illuminated 99%, and is located in Pisces on October 1st at 0:00 UT. The Moon reaches its greatest northern declination (+24.5 degrees) on October 10th and its greatest southern declination (-24.7 degrees) on October 22nd. Longitudinal libration is at a maximum of +7.7 degrees on October 23rd and a minimum of -7.7 degrees on October 11th. Latitudinal libration is at a maximum of +6.6 degrees on October 1st and +6.7 degrees on October 28th and a minimum of -6.6 degrees on October 15th. Favorable librations for the following lunar features occur on the indicated dates: Crater Focas on October 12th, Crater Rydberg on October 13th, Crater Goddard on October 22nd, and Crater Boss on October 24th. There are two Full Moons this month, resulting in the second one being referred to by one definition as a Blue Moon. New Moon occurs on October 16th. Large tides will occur for several days thereafter. The Moon is at apogee (at a distance of 63.70 Earth-radii) on October 3rd and again (at a distance of 63.72 Earth-radii) on October 30th and at perigee (a distance of 55.96 Earth-radii) on October 16th. The Moon occults Mars from some parts of the world on October 3rd. Consult http://www.lunar-occ...ota/iotandx.htm for further information on lunar occultation events. Visit https://saberdoesthe...does-the-stars/ for tips on spotting extreme crescent Moons and http://www.curtrenz.com/moon06.html for Full Moon data. Consult http://time.unitariu...moon/where.html or download http://www.ap-i.net/avl/en/start for current information on the Moon. Visit https://www.fourmila...odMJtNWK1OLMxYk for a list of lunar maria and https://upload.wikim...tCZImsof8HUNAKI for a simple map of the Moon showing the most prominent maria. See https://svs.gsfc.nasa.gov/4768 for a lunar phase and libration calculator and https://quickmap.lro...2vIBvAXwF1SizSg for the Lunar Reconnaissance Orbiter Camera (LROC) Quickmap. Click on https://www.calendar...ar/2020/october for a lunar phase calendar for this month. Times and dates for the lunar crater light rays predicted to occur this month are available at http://www.lunar-occ...o/rays/rays.htm
The Sun is located in Virgo on October 1st at 0:00 UT. It enters Libra at 19:00 UT on October 30th.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on October 1st: Mercury (magnitude 0.0, 6.7", 61%, 1.00 a.u., Virgo), Venus (magnitude -4.1, 15.5", 72%, 1.07 a.u., Leo), Mars (magnitude -2.5, 22.4", 99%, 0.42 a.u., Pisces), Jupiter (magnitude -2.4, 40.5", 99%, 4.86 a.u., Sagittarius), Saturn (magnitude +0.5, 17.2", 100%, 9.66 a.u., Sagittarius), Uranus (magnitude +5.7, 3.7", 100%, 18.82 a.u. on October 16th, Aries), Neptune (magnitude +7.8, 2.3", 100%, 29.10 a.u. on October 16th, Aquarius), and Pluto (magnitude +14.3, 0.1", 100%, 34.14 a.u. on October 16th, Sagittarius).
This month Mercury is located in the west, Mars and Uranus in the east, Jupiter and Saturn in the south, and Neptune in the southeast during the evening. At midnight, Mars and Neptune can be found in the south and Uranus in the southeast. Venus is in the east and Mars and Uranus are in the west in the morning sky.
Mercury reaches greatest eastern elongation on October 1st and greatest heliocentric latitude south on October 9th. A very thin crescent Moon passes seven degrees north of Mercury on October 17th. The speediest planet grows fainter and drops lower in the western sky as it heads towards inferior conjunction on October 25th.
Venus maintains its brilliance this month as it decreases in angular diameter from 15.5 to 13.2 arc seconds while increasing in illumination from 72 to 81%. Venus and Regulus undergo a very close appulse on October 2nd and October 3rd. The two celestial objects are closest at 2:00 p.m. EDT (18:00 UT) on October 2nd. The waning crescent Moon passes four degrees to the north of Venus on October 13th.
On October 6th, Mars makes its closest approach to the Earth until 2035. On that date, Mars will span 22.6 arc seconds, 87% of its maximum size, and shine brighter than Jupiter at magnitude -2.6. It has appeared brighter and larger only twice, in 2003 and 2018, since 1988. The Red Planet reaches opposition a week later at 7:20 p.m. EDT (23:20 UT) due to the asymmetric nature of the 2020 apparition. Mars will be 5.5 degrees north of the celestial equator, making it 31 degrees higher in altitude for northern hemisphere observers than it was during the somewhat closer 2018 opposition. Mars will be 55 degrees in altitude for observers at 40 degrees north at midnight on the night of opposition. The Martian south pole is favorably inclined 20.4 degrees towards the Earth on October 13th. Mars rotates 9.1 degrees westward each day, which means different surface features are visible throughout a month. The most prominent Martian surface features include Syrtis Major, the Hellas basin, Elysium, Chryse, Libya, and Solis Lacus. Syrtis Major and the Hellas basin are located near the center of the Martian disk at 12:00 a.m. EDT from October 5th through October 9th. During the second half of the month, the volcano Elysium Mons may appear as a bright spot. The dark feature Mare Cimmerium lies to the south. The gigantic volcano Olympus Mons and the Tharsis ridge are on the central meridian around October 25th, with Mare Sirenum to the south. As the month draws to a close, Valles Marineris and Solis Lacus, the aptly-named Eye of Mars, appear centrally. Mars will decrease in brightness to magnitude -2.2 and shrink in apparent size to 20.2 arc seconds by the end of October. As Mars retrogrades through Pisces this month, reaching a position three degrees south of the fourth-magnitude star Epsilon Piscium on October 31st, it has two conjunctions with the almost Full Moon, one on the night of October 2nd/October 3rd and the other on October 29th. At their greatest elongations, the tiny Martian satellites Deimos (magnitude +11.7) and Phobos (magnitude +10.8) are 67 and 20 arc seconds from Mars respectively. Articles on Mars at opposition appear on pages 44 to 47 of the October issue of Astronomy and pages 48 to 50 of the October 2020 issue of Sky & Telescope. Click on https://skyandtelesc...ide-is-visible/ in order to determine what Martian surface features are visible.
Jupiter fades slightly to magnitude -2.2 and decreases in apparent size to 37.1 arc seconds this month. It sets by 11:00 p.m. local time on October 31st. Jupiter is at eastern quadrature on October 11th. Eclipses of the Galilean satellites will be enhanced as a result. A double Galilean satellite shadow transit takes place on October 17th. The waxing gibbous Moon passes two degrees south of Jupiter on October 22nd. Information on Great Red Spot transit times and Galilean satellite events is available on pages 52 and 53 of the October 2020 issue of Sky & Telescope and online at http://www.skyandtel...watching-tools/ and https://www.projectp....com/jevent.htm
Saturn sets by 11:00 p.m. local time as October ends. The Ringed Planet’s disk is 17 arc seconds in angular diameter and its rings measure 38 arc seconds this month. On October 1st, Saturn lies seven degrees east of Jupiter. Both planets are now undergoing prograde or eastward motion so the gap between them decreases to just five degrees by the end of October. Saturn reaches eastern quadrature on October 18th, which results in the planet having a more three-dimensional appearance. The waxing crescent Moon passes three degrees south of Saturn on October 23rd. For information on Saturn’s satellites, browse https://skyandtelesc...script-utility/
Uranus is located 1.2 degrees southwest of the sixth-magnitude star 29 Arietis on October 1st. Retrograde motion carries the ice giant 2.3 degrees from the star by month's end. Uranus reaches opposition on October 31st, it is 2.6 light hours from the Earth and shines at magnitude +5.7, which is bright enough to be visible without optical aid from a dark site. The waning gibbous Moon passes three degrees south of the ice giant on October 4th. Visit http://www.nakedeyep....com/uranus.htm for a finder chart.
Neptune travels from 1.6 degrees east-northeast of the fourth-magnitude star Phi Aquarii to just 57 arc minutes from the star during October. The waning gibbous Moon passes four degrees south of Neptune on October 27th. Browse http://www.nakedeyep...com/neptune.htm for a finder chart. An article on Neptune complete with finder charts appears on page 48 of the September 2020 issue of Sky & Telescope. Triton, Neptune's brightest satellite, can be located using the Sky & Telescope interactive observing tool at https://skyandtelesc...triton-tracker/
The dwarf planet Pluto can be found near the Teaspoon asterism in northeastern Sagittarius at a declination of -22.65 degrees. Finder charts can be found at pages 48 and 49 of the July 2020 issue of Sky & Telescope and on page 243 of the RASC Observer’s Handbook 2020.
For more on the planets and how to locate them, see http://www.nakedeyeplanets.com/
The Distance, Brightness, and Apparent Size of Planets graphic at https://www.timeandd...lanets/distance displays the apparent and comparative sizes of the planets, along with their
magnitudes and distances, on a given date and time.
Comet P/Howell heads eastward through Scorpius and Sagittarius this month. The period comet passes south of the globular cluster M19 on October 5th, south of the globular cluster NGC 6293 on October 6th, south of the globular cluster NGC 6355 on October 10th, south of the dark nebula LDN 1773 (the Pipe Nebula) on October 11th through October 13th, and north of the open cluster NGC 6520 on October 19th. Browse http://www.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://www.britastro...arts_comet.html
On October 30th, asteroid 8 Flora is less than 10 arc minutes west of Gamma Ceti (magnitude +3.5). On the following day, the eighth-magnitude asteroid is just 209,000 kilometers (130,000 miles) from the Earth, the closest approach to our planet during the period from 1980 to 2060. During October, asteroid 19 Fortuna shines at tenth magnitude as it travels southward through Aquarius, about 1.5 degrees north of the fourth-magnitude star Lambda Aquarii. Asteroid 11 Parthenope (magnitude +9.4) reaches opposition on October 23rd. Three days later asteroid 471 Papagena (magnitude +9.5) does the same. Other asteroids brighter than magnitude +11.0 coming to opposition this month include 747 Winchester (magnitude +10.4) on October 13th, 194 Prokne (magnitude +10.7), and 67 Asia (magnitude +10.8) on October 24th. Data on asteroid occultations taking place this month is available at http://www.asteroido.../2020_10_si.htm and http://www.poyntsour.../New/Global.htm
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in brightness from magnitude +2.1 to magnitude +3.4, on October 1st, 4th, 6th, 9th, 12th, 15th, 18th, 21st, 24th, 27th, and 29th. Consult page 51 of the October 2020 issue of Sky & Telescope for the minima times. On the night of October 3rd, Algol shines at minimum brightness (magnitude +3.4) for approximately two hours centered at 9:48 p.m. EDT (1:48 UT October 4th). It does the same at 2:40 p.m. EDT (6:40 UT October 21st) on the night of October 21st, at 11:29 p.m. EDT (3:29 UT on October 24th) on the night of October 23rd, and 8:18 p.m. EDT (0:18 UT October 27th) on October 26th. For more on Algol, see http://stars.astro.i.../sow/Algol.html and http://www.solstatio...ars2/algol3.htm
Data on current supernovae can be found at http://www.rochester...y.org/snimages/
Finder charts for the Messier objects and other deep-sky objects are posted at http://www.freestarcharts.com/messier and http://www.freestarcharts.com/ngc-ic and http://www.cambridge...er-december.htm
Telrad finder charts for the Messier Catalog are posted at http://www.custerobs...cs/messier2.pdf
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
A freeware sky atlas can be downloaded at http://www.deepskywa...-atlas-full.pdf
Eighty-five binary and multiple stars for October: Struve 2973, Struve 2985, Struve 2992, Struve 3004, Struve 3028, Otto Struve 501, Struve 3034, Otto Struve 513, Struve 3050 (Andromeda); 29 Aquarii, 41 Aquarii, 51 Aquarii, 53 Aquarii, Zeta Aquarii, Struve 2913, Struve 2935, Tau-1 Aquarii, Struve 2944, Struve 2988, Psi-1 Aquarii, 94 Aquarii, 96 Aquarii, h3184, Omega-2 Aquarii, 107 Aquarii (Aquarius); Otto Struve 485, Struve 3037, 6 Cassiopeiae, Otto Struve 512, Sigma Cassiopeiae (Cassiopeia); Xi Cephei, Struve 2883, Struve 2893, Struve 2903, Krueger 60, Delta Cephei, Struve 2923, Otto Struve 482, Struve 2947, Struve 2948, Struve 2950, Struve 2984, Omicron Cephei, Otto Struve 502 (Cepheus); Otto Struve 459, h1735, Struve 2876, Otto Struve 465, Struve 2886, Struve 2894, h1756, Struve 2902, Struve 2906, 8 Lacertae, Otto Struve 475, 13 Lacertae, h1828, 16 Lacertae (Lacerta); Struve 2857, Struve 2877, 34 Pegasi, Struve 2908, Xi Pegasi, Struve 2958, Struve 2978, 57 Pegasi, Struve 2991, h1859, Struve 3007, Struve 3021, Otto Struve 504, Struve 3044 (Pegasus); Struve 3009, Struve 3019, Struve 3033 (Pisces); Eta Piscis Austrini, Beta Piscis Austrini, Dunlop 241, h5356, Gamma Piscis Austrini, Delta Piscis Austrini, h5371 (Piscis Austrinus); h5417, Delta Sculptoris, h5429 (Sculptor)
Notable carbon star for October: RZ Pegasi
Seventy-five deep-sky objects for October: NGC 7640, NGC 7662, NGC 7686 (Andromeda); NGC 7180, NGC 7183, NGC 7184, NGC 7293, NGC 7392, NGC 7585, NGC 7606, NGC 7721, NGC 7723, NGC 7727 (Aquarius); Cz43, K12, M52, NGC 7635, NGC 7788, NGC 7789, NGC 7790, St12 (Cassiopeia); B171, B173-4, IC 1454, IC 1470, K10, Mrk50, NGC 7235, NGC 7261, NGC 7354, NGC 7380, NGC 7419, NGC 7510 (Cepheus); IC 1434, IC 5217, NGC 7209, NGC 7223, NGC 7243, NGC 7245 (Lacerta); NGC 7177, NGC 7217, NGC 7320 (the brightest galaxy in Stephan's Quintet), NGC 7331, NGC 7332, NGC 7339, NGC 7448, NGC 7454, NGC 7479, NGC 7619 (the brightest member of Pegasus I), NGC 7626, NGC 7678, NGC 7742, NGC 7769 (Pegasus); NGC 7541, NGC 7562, NGC 7611 (Pisces); IC 5156, IC 5269, IC 5271, NGC 7172, NGC 7173, NGC 7174, NGC 7176, NGC 7201, NGC 7203, NGC 7214, NGC 7221, NGC 7229, NGC 7314, NGC 7361 (Piscis Austrinus); NGC 7507, NGC 7513, NGC 7713, NGC 7755, NGC 7793 (Sculptor)
Top ten binocular deep-sky objects for October: M52, NGC 7209, NGC 7235, NGC 7243, NGC 7293, NGC 7510, NGC 7686, NGC 7789, NGC 7790, St12
Top ten deep-sky objects for October: K12, M52, NGC 7209, NGC 7293, NGC 7331, NGC 7332, NGC 7339, NGC 7640, NGC 7662, NGC 7789
Challenge deep-sky object for October: Jones 1 (PK104-29.1) (Pegasus)
The objects listed above are located between 22:00 and 24:00 hours of right ascension.