July Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
7/1 Last Quarter Moon occurs at 21:11
7/3 The Curtiss Cross, an X-shaped clair-obscur illumination effect located between the craters Parry and Gambart, is predicted to be visible at 11:24; Venus is 0.4 degrees north-northeast of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 12:00
7/4 Venus is at its northernmost latitude from the ecliptic plane (3.4 degrees) at 3:00; the Moon is 1.9 degrees south-southeast of Uranus at 18:00; Mercury is at its greatest western elongation (22 degrees) at 20:00
7/5 The Moon is at apogee; subtending 29' 29" from a distance of 405,341 kilometers (251,867 miles) at 14:47; Earth is at aphelion (152,100,527 kilometers from the Sun) at 22:00
7/6 The Moon is 5.0 degrees southeast of the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 4:00; the Moon is 5.4 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 22:00; the Moon is at the ascending node (longitude 70.5 degrees) at 23:00
7/8 The Moon is 3.7 degrees north of Mercury at 4:00; the Moon is 1.0 degrees north of the bright open cluster M35 in Gemini at 19:00
7/10 New Moon (lunation 1219) occurs at 1:17; the Moon is 6.7 degrees south of the first-magnitude star Castor (Alpha Geminorum) at 8:00; the Moon is 3.2 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 13:00
7/11 The Moon is 3.1 degrees north-northeast of M44 at 15:00
7/12 The Moon is 3.1 degrees north-northeast of Venus at 12:00; the Moon, Venus, and Mars lie within a circle with a diameter of 3.6 degrees at 12:00; the Moon 3.6 degrees north-northeast of Mars at 13:00
7/13 Mars is at aphelion (1.6660 astronomical units from the Sun) at 00:00; the Moon is 4.6 degrees north-northeast of the first-magnitude star Regulus (Alpha Leonis) at 9:00; Venus is 0.5 degrees north-northeast of Mars at 14:00; Mercury is 2.2 degrees south of M35 at 15:00
7/16 The Lunar X, also known as the Werner or Purbach 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 fully formed at 23:02
7/17 The Moon is 5.7 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 10:00; First Quarter Moon occurs at 10:11; the S-type asteroid 6 Hebe (magnitude +8.4) is at opposition in Aquila at 11:00; Pluto is at opposition (apparent size 0.1", magnitude +14.3) at 23:00
7/18 The B-type asteroid 2 Pallas (magnitude +9.7) is stationary in Pisces at 20:00
7/19 Mercury is at the ascending node through the ecliptic plane at 9:00
7/20 Mercury is at its northernmost declination (22.9 degrees) today; the Moon is at the descending node (longitude 249.8 degrees) at 13:00; the Moon is 4.5 degrees north-northeast of Antares at 15:00; the Sun enters Cancer, at longitude 118.3 degrees on the ecliptic, at 19:00
7/21 The Moon is at perigee, subtending 32' 47" at a distance of 364,523 kilometers (226,503 miles) at 10:24
7/22 Venus is 1.1 degrees north-northeast of Regulus at 4:00; the Sun's longitude is 120 degrees at 14:00
7/23 Mercury is 9.3 degrees south of Castor at 21:00
7/24 Mercury is at perihelion (0.3075 astronomical units from the sun) at 1:00; Full Moon, known as the Hay or Thunder Moon, occurs at 2:37; the Moon is 3.7 degrees southeast of Saturn at 19:00
7/25 Mercury is 5.7 degrees south of Pollux at 4:00; the equation of time is at a minimum of -6.55 minutes at 23:00
7/26 The Moon is 3.9 degrees southeast of Jupiter at 5:00
7/27 The Moon is 3.8 degrees southeast of Neptune at 22:00
7/29 The peak of the Southern Delta Aquarid meteor shower (a zenithal hourly rate of 20 per hour) is predicted to occur at 5:00; a double Galilean satellite shadow transit (Callisto's shadow precedes Io's) begins at 20:06
7/30 Mars is 0.6 degrees north-northeast of Regulus at 2:00; the S-type asteroid 12 Victoria (magnitude +8.8) is at opposition in Aquila at 13:00
7/31 Last Quarter Moon occurs at 13:16; Mercury is 0.4 degrees north-northeast of M44 at 17:00
Friedrich Bessel (1784-1846) was born this month.
The light from Supernova SN 1054 was first noted by Chinese astronomers on July 4, 1054. The first lunar map was drawn by Thomas Harriot on July 26, 1609. Charles Messier discovered the globular cluster M28 in Sagittarius on July 27, 1764. Comet D/1770 L1 (Lexell) passed closer to the Earth than any comet in recorded history on July 1, 1770. Charles Messier discovered the globular cluster M54 in Sagittarius on July 24, 1778. Caroline Herschel discovered the open cluster NGC 6866 in Cygnus on July 23, 1783. The globular cluster NGC 6569 in Sagittarius was discovered by William Herschel on July 13, 1784. Karl Ludwig Hencke discovered asteroid 6 Hebe on July 1, 1847. The first photograph of a star, namely Vega, was taken on July 17, 1850. The first photograph of a total solar eclipse was taken on July 28, 1851. Hendri Deslandres invented the spectroheliograph on July 24, 1853. Sinope, one of Jupiter’s many satellites was discovered by Seth Nicholson on July 21, 1914. Karl Jansky announced the detection of radio radiation from the center of the Milky Way on July 8, 1933. Seth Nicholson discovered Neptune’s satellite Lysithea on July 6, 1938. The Mariner 4 probe took the first close-up image of another planet, namely Mars, on July 14, 1965. The Apollo 11 lunar module landed on the Moon on July 20, 1969. Neptune’s satellites Despinea and Galatea are discovered using images from the Voyager 2 probe on July 27, 1989. Fragments of Comet D/1993 F2 (Shoemaker-Levy) impacted Jupiter on July 16, 1994. Prospero, one of the satellites of Uranus, is discovered by Matthew Holman on July 18, 1999. Pluto’s satellite Styx is discovered using images from the New Horizon probe on July 11, 2012.
The peak of the Southern Delta Aquarid meteor shower on the morning of July 29th is compromised by moonlight from a waning gibbous Moon. The radiant is located northwest of the first-magnitude star Fomalhaut (Alpha Piscis Austrini). Jupiter lies about four degrees north of the radiant this year. Southern hemisphere observers are favored. Click on https://earthsky.org...-meteor-shower/ for further information. The Alpha Capricornids, the Piscis Austrinids, and the Northern Delta Aquarids are the other minor meteor showers with southern radiants occurring this month. A list of the year's meteor showers appears on page 254 of the RASC's Observer's Handbook 2021.
Information on passes of the ISS, the USAF’s X-37B, the HST, Starlink, and other satellites can be found at http://www.heavens-above.com/
The Moon is 20.4 days old, is illuminated 60.4%, subtends 30.2 arc minutes, and is located in Pisces on July 1st at 0:00 UT. The Moon is at its greatest northern declination of +25.5 degrees on July 9th and its greatest southern declination of -25.5 degrees on July 23rd. Longitudinal libration is at a maximum of +6.2 degrees on July 27th and a minimum of -5.6 degrees on July 14th. Latitudinal libration is at a maximum of +6.6 degrees on July 27th and a minimum of -6.7 degrees on July 14th. Favorable librations for the following lunar features occur on the indicated dates: Crater Lagrange on July 8th, Crater Belkovich on July 22nd, Mare Humboldtianum on July 23rd, and Crater Compton on July 24th. New Moon takes place on July 20th. The Moon is at apogee (a distance 63.55 Earth-radii) on July 5th and at perigee (distance 57.15 Earth-radii) on July 21st. Browse 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...vIBvAXwF1SizSg for the Lunar Reconnaissance Orbiter Camera (LROC) Quickmap. Click on https://www.calendar...endar/2021/july 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 Gemini on July 1st. The Earth is farthest from the Sun, a distance of 1.0167 astronomical units, on July 5th. On that date, it is 3.3% more distant than it was at perihelion and 1.7% farther than its average distance. The Sun enters Cancer on July 20th.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on July 1st: Mercury (+0.8 magnitude, 8.8", 27% illuminated, 0.77 a.u., Taurus), Venus (-3.8 magnitude, 11.2", 90% illuminated, 1.49 a.u., Cancer), Mars (+1.8 magnitude, 3.9", 97% illuminated, 2.43 a.u., Cancer), Jupiter (-2.6 magnitude, 45.3", 99% illuminated, 4.36 a.u., Aquarius), Saturn (+0.4 magnitude, 18.3", 100% illuminated, 9.09 a.u., Capricornus), Uranus (+5.8 magnitude, 3.5", 100% illuminated, 20.08 a.u. on July 16th, Aries), Neptune (+7.9 magnitude, 2.3", 100% illuminated, 29.39 a.u. on July 16th, Aquarius), and Pluto (+14.3 magnitude, 0.1", 100% illuminated, 33.37 a.u. on July 16th, Sagittarius).
Venus and Mars are in the west and Jupiter and Saturn are in the east during the evening. At midnight, Jupiter and Saturn are in the southeast, and Neptune is in the east. In the morning, Mercury and Uranus can be found in the east, Jupiter and Neptune in the south, and Saturn in the southwest.
On July 4th, Mercury achieves greatest western elongation. A waning crescent Moon passes four degrees north of the planet on the morning of July 8th. Mercury is at its most northerly latitude from the ecliptic plane on July 20th and is at perihelion on July 24th.
Venus changes very little in brightness, apparent size, and illumination during July. Venus increases in solar elongation from 25 to 33 degrees but a 12-degree decline in declination leaves it poorly placed. The brightest planet passes north of the open cluster M44 on July 3th and is at its greatest northern latitude the next day. Venus and Mars both travel southeastward through Leo this month coming within 0.5 degrees of each other on July 13th. The waxing crescent Moon passes three degrees north of the two rocky planets on July 11th and July 12th. Venus passes about four degrees south of the barred-spiral galaxy M95 on July 27th.
Mars is only 3.7 arc seconds in apparent size and, at magnitude +1.8, is near its minimum brightness. Its elongation from the Sun decreases from 33 to 22 degrees this month. The waning gibbous Moon passes two degrees south of the Red Planet on July 11th. Mars is at aphelion on July 13th and is also 0.5 degrees south of Venus on that date. Mars enters Leo in mid-July. It passes less than one degree north of Regulus on July 29th.
Jupiter rises before midnight as it retrogrades through Aquarius this month. It subtends 48.4 arc seconds and shines at magnitude -2.8 on the final day of July. A waning gibbous Moon passes less than four degrees to the south of the gas giant planet on the night of July 25th/26th. Io eclipses Europa from 10:54 to 10:57 UT on July 5th. Callisto and the shadow of Europa both transit Jupiter on the morning of July 25th. Io disappears into eclipse not long afterwards. A double Galilean shadow transit involving the shadows of Callisto and Io takes place from some parts of the world on July 29th. Information on Great Red Spot transit times and Galilean satellite events is available on pages 50 and 51 of the July 2021 issue of Sky & Telescope and online at http://www.skyandtel...watching-tools/ and https://www.projectp....com/jevent.htm
Saturn rises around 10:00 p.m. local time and reaches the meridian about 3:00 a.m. local time on July 1st. It brightens to magnitude +0.2 and subtends 18.6 arc seconds by the end of July. Its rings span 42 arc seconds. Saturn passes one arc minute north of the faint barred-spiral galaxy IC 1339 on the night of July 4th/July 5th. On July 24th, the Full Moon passes four degrees south of the Ringed Planet. An article on observing elusive features in the Saturnian rings can be found on pages 52 and 53 of the July 2021 issue of Sky & Telescope. Saturn's largest and brightest satellite Titan (magnitude +8.5) lies due north of Saturn on July 2nd and July 18th and due south of the planet on July 10th and July 26th. When the faint Saturnian satellite Iapetus attains western elongation on July 4th, it's positioned nine arc minute due west of Saturn and shines at tenth magnitude. For further data on Saturn’s satellites, browse http://www.skyandtel...watching-tools/
Uranus is located 12 arc minutes due north of the sixth-magnitude star Omicron Arietis on July 1st. By July 31st, the ice giant planet has traveled to a position almost one degree northeast of the star. A waning crescent Moon passes less than five degrees southeast of Uranus on July 4th. Visit http://www.nakedeyep....com/uranus.htm for a finder chart.
Neptune rises around local midnight as it retrogrades through eastern Aquarius. The eighth planet is located about six degrees east of the fourth-magnitude star Phi Aquarii and very close to the seventh-magnitude field star HIP 116402. A gibbous Moon passes eight degrees southwest of Neptune on July 27th. Browse http://www.nakedeyep...com/neptune.htm for a finder chart.
The dwarf planet Pluto reaches opposition on July 15th. Finder charts can be found on pages 48 and 49 of the July 2021 issue of Sky & Telescope and on page 243 of the RASC Observer’s Handbook 2021. An article on observing Pluto appears on pages 46 to 49 of the July 2021 issue of Astronomy.
For more on the planets and how to locate them, browse http://www.nakedeyeplanets.com/
The periodic comet 4P/Faye travels northeastward through Aries during July. The tenth-magnitude comet passes less than two degrees to the north of Uranus on July 18th and July 19th. Visit http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html and https://cobs.si/ for information on comets visible this month.
Asteroid 4 Vesta heads southeastward from Leo into Virgo this month. The main belt asteroid lies within one degree of the fifth-magnitude star Pi Virginis for five nights centered on July 13th. It passes 20 arc seconds south of the spiral galaxy M61 on July 27th. Asteroid 6 Hebe (magnitude +8.4) is at opposition on July 17th and asteroid 12 Victoria (magnitude +8.8) is at opposition on July 30th. A finder chart for 6 Hebe appears on page 50 of the July 2021 issue of Sky & Telescope. Information on asteroid occultations taking place this month is available at https://www.asteroid.../2021_07_si.htm
Data on current supernovae can be found at http://www.rochester...y.org/snimages/
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
Forty binary and multiple stars for July: Eta Draconis, 17 & 16 Draconis, Mu Draconis, Struve 2273, Nu-1 & Nu-2 Draconis, Psi Draconis (Draco); Kappa Herculis, Gamma Herculis, Struve 2063, 56 Herculis, Struve 2120, Alpha Herculis (Ras Algethi), Delta Herculis, Rho Herculis, Mu Herculis (Hercules); Rho Ophiuchi, Lambda Ophiuchi, 36 Ophiuchi, Omicron Ophiuchi, Burnham 126 (ADS 10405), Struve 2166, 53 Ophiuchi, 61 Ophiuchi (Ophiuchus); h5003 (Sagittarius); Xi Scorpii, Struve 1999, Beta Scorpii, Nu Scorpii, 12 Scorpii, Sigma Scorpii, Alpha Scorpii (Antares), h4926 (Scorpius); Struve 2007, 49 Serpentis, Struve 2031 (Serpens Caput); 53 Serpentis, Struve 2204, h4995, h2814 (Serpens Cauda); Epsilon Ursae Minoris (Ursa Minor)
Notable carbon star for July: T Draconis
Sixty-five deep-sky objects for July: NGC 6140, NGC 6236, NGC 6340, NGC 6395, NGC 6412, NGC 6503, NGC 6543 (Draco); IC 4593, M13, M92, NGC 6106, NGC 6166, NGC 6173, NGC 6181, NGC 6207, NGC 6210, NGC 6229, NGC 6482 (Hercules); B61, B62, B63, B64, B72, IC 4634, IC 4665, LDN 42, LDN 1773, M9, M10, M12, M14, M19, M62, M107, NGC 6284, NGC 6287, NGC 6293, NGC 6304, NGC 6309, NGC 6356, NGC 6366, NGC 6369, NGC 6384, NGC 6401, Tr 26 (Ophiuchus); NGC 6440, NGC 6445 (Sagittarius); B50, B55, B56, Cr 316, M4, M6, M7, M80, NGC 6144, NGC 6153, NGC 6192, NGC 6231, NGC 6242, NGC 6302, NGC 6337, NGC 6451 (Scorpius); NGC 6217, NGC 6324 (Ursa Minor)
Top ten binocular deep-sky objects for July: IC 4665, LDN 1773, M4, M6, M7, M10, M12, M13, M92, NGC 6231
Top ten deep-sky objects for July: M4, M6, M7, M10, M12, M13, M92, NGC 6210, NGC 6231, NGC 6543
Challenge deep-sky object for July: NGC 6380 (Scorpius)
The objects listed above are located between 16:00 and 18:00 hours of right ascension.