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 The Moon is 3.3 degrees north-northeast of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 16:00; asteroid 40 Harmonia (magnitude +9.5) is at opposition in Cetus at 19:00
10/2 Mercury is 1.5 degrees south-southwest of the first-magnitude star Spica (Alpha Virginis) at 10:00
10/3 Venus is at aphelion (0.7282 astronomical units from the Sun) at 1:00; the Moon is 4.7 degrees north-northeast of the first-magnitude star Regulus (Alpha Leonis) at 10:00
10/4 A double Galilean shadow transit begins at 18:53
10/5 Pluto is stationary, with prograde or direct (eastward) motion to resume, at 22:00
10/6 New Moon (lunation 1222) occurs at 11:05; the Moon is 3.2 degrees north-northeast of Mars at 13:00; the Moon is 6.2 degrees north-northeast of Mercury at 23:00
10/7 The Moon is 5.3 degrees north-northeast of Spica at 6:00
10/8 Mars is in conjunction with the Sun (2.628 astronomical units from the Earth, latitude 1.0 degrees) at 4:00; the Moon is at perigee, subtending 32' 53" from a distance of 363,388 kilometers (225,797 miles), at 17:28; the dwarf planet/asteroid 1 Ceres is stationary at 19:00
10/9 Mercury is in inferior conjunction with the Sun (0.662 astronomical units from the Earth, latitude -3.7 degrees) at 16:00; the Moon is at the descending node (longitude 242.5 degrees) at 20:00; the Moon is 2.7 degrees north-northeast of Venus at 21:00
10/10 Mercury is 2.4 degrees southwest of Mars at 5:00; the Moon is 3.9 degrees north-northeast of the first-magnitude star Antares (Alpha Scorpii) at 9:00; Mercury, Mars, and Antares lie within a circle with a diameter of 4.3 degrees at 19:00
10/11 Saturn is stationary, with direct motion to resume, at 2:00
10/13 First Quarter Moon occurs at 3:25; the Lunar X, also known as the Purbach or Werner Cross, an X-shaped clair-obscur illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to be visible at 10:16; Pluto is at its southernmost declination (-22.9 degrees) at 16:00
10/14 The Moon is 3.8 degrees southeast of Saturn at 9:00
10/15 Mercury is at the ascending node through the ecliptic plane at 8:00; the Moon is 4.0 degrees southeast of Jupiter at 13:00
10/16 Venus is 1.4 degrees north-northeast of Antares at 21:00
10/17 The Moon is 3.7 degrees southeast of Neptune at 18:00
10/18 Mercury is stationary, with direct motion to resume at 1:00; Jupiter is stationary, with direct motion to resume, at 11:00
10/19 A double Galilean shadow transit begins at 6:12
10/20 Full Moon, known as the Blood or Sanguine Moon, occurs at 14:56
10/21 The peak of the Orionid meteor shower (a zenithal hourly rate of 20 per hour) is predicted to occur at 12:00; Mars is 2.6 degrees north-northeast of Spica at 21:00; the Moon is 1.2 degrees southeast of Uranus at 23:00
10/23 The Sun's longitude is 210 degrees at 5:00; the Moon is 4.2 degrees southeast of the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 10:00; the Moon is at the ascending node (longitude 61.9 degrees) at 12:00
10/24 The Moon is 6.2 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 4:00; the Moon is at apogee, subtending 29' 28" from a distance of 405,613 kilometers (252,038 miles), at 15:28
10/25 Venus is at its southernmost latitude from the ecliptic plane (-3.4 degrees) at 1:00; Mercury is at greatest western elongation (18 degrees) at 6:00
10/26 The Moon is 1.7 degrees north of the bright open cluster M35 in Gemini at 2:00; a double Galilean shadow transit begins at 8:08
10/27 The Moon is 6.2 degrees south of the first-magnitude star Castor (Alpha Geminorum) at 16:00; the Moon is 2.6 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 21:00
10/28 Venus is at dichotomy (illuminated 50%) at 14:00; Last Quarter Moon occurs at 20:05
10/29 The Moon is 3.5 degrees north-northeast of the bright open cluster M44 (the Beehive Cluster or Praesepe) at 0:00; the Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to be visible at 10:50; Venus is at greatest eastern elongation (47 degrees) at 21:00
10/30 Mercury is at its northernmost latitude from the ecliptic plane (7.0 degrees) at 5:00; Saturn is at eastern quadrature (90 degrees from the Sun) at 10:00; the Moon is 4.8 degrees north-northeast of Regulus at 19:00
10/31 The Sun enters Libra (longitude 217.8 degrees on the ecliptic) at 1:00
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 8th. The Draconids are quite variable and have produced meteor storms in 1933 and 1946. Comet 21P/Giacobini-Zimmer is the parent comet of the Draconids. Consult https://www.timeandd...r/draconid.html and https://earthsky.org...-meteor-shower/ for additional information on the Draconid meteor shower. The Orionid meteor shower peaks on the night of October 21st/22nd and is severely affected by an almost Full Moon. Orionid meteors are fragments of Comet 1P/Halley. Browse at https://www.timeandd...er/orionid.html and https://earthsky.org...d-meteor-shower for more on the Orionids.
Information on Iridium flares and passes of the ISS, the Tiangong, 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 roughly the first half of the month. Articles on the zodiacal light appear at www.atoptics.co.uk/highsky/zod1.htm and https://earthsky.org...t-or-false-dawn
The Moon is 23.8 days old, subtends 30.1 arc minutes, is illuminated 33%, and is located in Pisces on October 1st at 0:00 UT. The Moon reaches its greatest northern declination (+26.2 degrees) on October 27th and its greatest southern declination (-26.1 degrees) on October 12th. Longitudinal libration is at a maximum of +6.0 degrees on October 16th and a minimum of -6.2 degrees on October 3rd and -7.1 degrees on October 31st. Latitudinal libration is at a maximum of +6.7 degrees on October 16th and a minimum of -6.6 degrees on October 4th and -6.8 degrees on October 31st. Favorable librations for the following lunar features occur on the indicated dates: Crater Rydberg on October 3rd, Crater Riemann on October 12th, Crater Mercurius on October 16th, and Vallis Baade on October 31st. New Moon occurs on October 6th. The Moon is at perigee (a distance of 56.97 Earth-radii) on October 8th and at apogee (at a distance of 63.60 Earth-radii) on October 24th. Consult http://www.lunar-occ...ota/iotandx.htm for information on lunar occultation events. Visit https://saberdoesthe...does-the-stars/ for tips on spotting extreme crescent Moons and https://curtrenz.com/moon.html for Full Moon and other lunar data. Browse https://skyandtelesc...ads/MoonMap.pdf and https://nightsky.jpl...ObserveMoon.pdf for simple lunar maps. Click on http://astrostrona.pl/moon-map for an excellent online lunar map. Visit http://www.ap-i.net/avl/en/start to download the free Virtual Moon Atlas. Consult http://time.unitariu...moon/where.html for current information on the Moon and https://www.fourmila.../lunarform.html for information on various lunar features. See https://svs.gsfc.nasa.gov/4874 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/2021/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 1:00 UT on October 31st.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on October 1st: Mercury (magnitude +1.5, 9.5", 17%, 0.71 a.u., Virgo), Venus (magnitude -4.3, 18.8", 62%, 0.89 a.u., Libra), Mars (magnitude +1.7, 3.6", 100%, 2.64 a.u., Virgo), Jupiter (magnitude -2.7, 46.3", 99%, 4.26 a.u., Capricornus), Saturn (magnitude +0.5, 17.7", 100%, 9.42 a.u., Capricornus), Uranus (magnitude +5.7, 3.7", 100%, 18.80 a.u. on October 16th, Aries), Neptune (magnitude +7.8, 2.3", 100%, 29.07 a.u. on October 16th, Aquarius), and Pluto (magnitude +14.3, 0.1", 100%, 34.34 a.u. on October 16th, Sagittarius).
This month Venus is located in the southwest, Jupiter in the southeast, Saturn in the south, and Uranus and Neptune in the east during the evening. At midnight, Jupiter and Saturn can be found in the southwest, Uranus in the southeast, and Neptune in the south. Mercury is in the east and Uranus is in the west in the morning sky.
Due to the favorable tilt of the fall ecliptic, Mercury undergoes the best morning apparition of 2021 for northern hemisphere observers in October. Mercury reaches inferior conjunction on October 9th and is lost in the Sun's glare until the second half of the month. It's at the ascending node on October 15th and at perihelion three days later. Mercury and the third-magnitude binary star Porrima (Gamma Virginis) rise together in the east on October 20th. On October 21st, Mercury attains an altitude of almost five degrees an hour before sunrise and shines at magnitude zero. The speediest planet is at greatest western elongation on October 25th and greatest heliocentric latitude north on October 30th. On the morning of October 31st, Mercury lies less than five degrees above Spica. Mercury brightens to magnitude -0.8 by the end of the month.
Because of its southerly declination, Venus is poorly placed for observers in the northern hemisphere this month. The brightest of the planets is at aphelion on October 3rd. The Moon passes 2.7 degrees north-northeast of Venus on October 9th. Venus is at heliocentric latitude south on October 25th, at dichotomy on October 28th, and at easternmost elongation on October 29th.
Mars is in solar conjunction on October 8th and is too close to the Sun to observe this month.
Jupiter fades slightly from magnitude -2.7 to magnitude -2.5 and decreases in angular diameter from 46.3 arc seconds to 42.3 arc seconds this month. It sets by 1:15 a.m. local time on October 31st. Jupiter's retrograde motion slows during the first half of the month. The largest planet lies 1.8 degrees northwest of the third-magnitude star Deneb Algedi (Delta Capricorni) on October 1st. After reaching its second stationary point on October 18th, the planet's motion becomes prograde or direct. On that date, Jupiter is 2.1 degrees northwest of the star but by the end of October Jupiter is just 1.9 degrees from the Deneb Algedi. The waxing gibbous Moon passes four degrees south of Jupiter on October 15th. The Galilean satellite Io emerges from eclipse at 9:48 p.m. EDT on October 5th. Europa is occulted by Jupiter 26 minutes later. On the night of October 12th/13th, Callisto begins to disappear into eclipse at 11:11 p.m. EDT, Io reappears from eclipse at 11:43 p.m. EDT, and Europa is occulted at 12:40 a.m. EDT. Io reappears from eclipse six arc minutes northwest of Europa at 10:03 p.m. EDT on October 28th. Double Galilean satellite shadow transits take place on October 4th, October 19th, and October 26th. Information on Great Red Spot transit times and Galilean satellite events is available on pages 50 and 51 of the October 2021 issue of Sky & Telescope and online at http://www.skyandtel...watching-tools/ and https://www.projectp....com/jevent.htm
Saturn sets around 2:00 a.m. local time as October begins and shortly before midnight on October 31st. The Ringed Planet’s disk is 17 arc seconds in angular diameter and its rings measure 38 arc seconds this month. Titan, Saturn's brightest satellite, shines at magnitude +8.5. It's located north of the planet on October 5th and October 21st and south of it on October 13th and October 29th. Saturn's two-faced satellite Iapetus is in superior conjunction on October 10th and then travels eastward reaching greatest elongation on October 29th, when it will be positioned just eight arc minutes east of the planet. The waxing gibbous Moon passes four degrees south of Saturn on October 14th. For information on Saturn’s satellites, browse https://skyandtelesc...script-utility/
Uranus is located just 23 arc minutes from the sixth-magnitude star Omicron Arietis on October 1st. Uranus is less than ten arc minutes north of the star on October 10th. By October 24th, the planet's westward motion places Uranus about 30 arc minutes west of Omicron Arietis. The waning gibbous Moon passes a bit more than one degree south of the ice giant on October 21st. Visit www.nakedeyeplanets.com/uranus.htm for a finder chart. Five of the brightest Uranian satellites (Miranda, Ariel, Umbriel, Titania, and Oberon) can be located using the Sky & Telescope interactive observing tool at https://skyandtelesc...moons-ofuranus/
Neptune lies less than four degrees east of the fourth-magnitude star Phi Aquarii at the month begins. It's situated 3.3 degrees from the star on October 31st. The waxing gibbous Moon passes about four degrees south of Neptune on October 17th. Browse www.nakedeyeplanets.com/neptune.htm for a finder chart. An article on Neptune complete with a finder chart appears on pages 48 and 49 of the September 2021 issue of Sky & Telescope. Triton, Neptune's brightest satellite, can be located using the Sky & Telescope interactive observing tool at https://skyandtelesc...triton-tracker/
Finder charts for Uranus and Neptune are also available at https://skyandtelesc...#comment-359616
Pluto is located to the southeast of the Teaspoon asterism in Sagittarius. It lies about six degrees to the southeast of the seventh-magnitude star HIP 97138 (SAO 188509). The dwarf planet is stationary on October 5th and reaches a southernmost declination of -22.9 degrees on October 13th. Finder charts can be found at pages 48 and 49 of the July 2021 issue of Sky & Telescope and on page 243 of the RASC Observer’s Handbook 2021.
For more on the planets and how to locate them, see https://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, for a given date and time.
Comet 67P/Churyumov-Gerasimenko passes northeastward through Taurus and into Gemini this month. The periodic comet passes one degree north of M1 (the Crab Nebula) on October 8th, north of the open cluster NGC 2129 on October 14th, and through the northern portion of the bright open cluster M35 on October 16th. An anti-tail may be visible at the end of the month when the comet will be seen edge-on. Another periodic comet, 4P/Faye, heads southeastward about eight degrees to the south of 67P/Churyumov-Gerasimenko. Comet C/2019 L3 (ATLAS) is located a similar distance to the northeast of 67P/Churyumov-Gerasimenko. All three comets are rather faint, shining at tenth to eleventh magnitude. Visit http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html and https://cobs.si/ for additional information on comets visible this month.
Asteroid 2 Pallas heads southwestward through Aquarius. The ninth-magnitude asteroid passes approximately one degree west of the fourth-magnitude star Lambda Aquarii on October 14th. Asteroid 40 Harmonia shines at magnitude +9.5 when it reaches opposition in Cetus to the southeast of the sixth magnitude binary star HR174 on October 1st. Asteroids brighter than magnitude +11.0 coming to opposition this month include 141 Lumen on October 14th, 50 Virginia on October 15th, and 25 Phocaea on October 18th. Data on asteroid occultations taking place this month is available at https://www.asteroid.../2021_10_si.htm and http://www.poyntsour.../New/Global.htm
An online data generator for various astronomical events is available at https://astronomynow.com/almanac/
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 3rd, 6th, 8th, 11th, 14th, 17th, 20th, 23rd, 26th, 29th, and 31st. Consult page 50 of the October 2021 issue of Sky & Telescope for the minima times. On the night of October 5th, Algol shines at minimum brightness (magnitude +3.4) for approximately two hours centered at 10:13 p.m. EDT (2:13 UT October 6th). It does the same at 11:54 p.m. EDT (3:54 UT on October 26th) on the night of October 25th, and 8:43 p.m. EDT (0:43 UT October 29th) on October 28th. 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 https://www.rocheste...y.org/snimages/
Information pertaining to observing some of the more prominent Messier galaxies can be found at https://www.cloudyni...ur-astronomers/
Telrad finder charts for the SAC’s 110 Best of the NGC are available at http://sao64.free.fr...ataloguesac.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
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.