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 The Moon is five degrees north of Mars at 2:00
7/4 The Moon is 2.4 degrees south-southeast of Neptune at 2:00; Mercury (magnitude +0.1) is 0.39 degree south-southwest of the bright open cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 13:00
7/5 Asteroid 3 Juno (magnitude +9.7) is 2.8 degrees south of Uranus (magnitude +5.8) at 7:13
7/6 Last Quarter Moon occurs at 7:51; the Earth is at aphelion (152,095,566 kilometers or 94,507,803 miles from the Sun) at 17:00; the Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to be visible at 20:43
7/7 The Moon is 4.7 degrees south-southeast of Uranus at 17:00; the Moon is 1.8 degrees south-southeast of asteroid 3 Juno at 17:38
7/9 The Moon is 8.8 degrees south-southeast of the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 18:00; Venus is 1.1 degrees north of the first-magnitude star Regulus (Alpha Leonis) at 20:00
7/10 Mercury is at the descending node at 1:00; the Moon is 1.1 degrees north-northwest of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation occurring in north-central Russia, most of Greenland, and central and northern North America at 9:00; Jupiter is stationary in longitude at 17:00
7/11 Jupiter is stationary in right ascension, with direct (eastward) motion to commence, at 4:00; the Moon is 3.8 degrees south of the bright open cluster M35 in Gemini at 22:00
7/12 Mercury is at greatest eastern elongation east (26.4 degrees) at 5:00; Pluto (magnitude +14.2, angular diameter 0.1") is at opposition at 10:00
7/13 New Moon (lunation 1182) occurs at 2:48; a partial solar eclipse reaches greatest eclipse at 3:01:07; the Moon is at perigee, subtending 33' 26" at a distance of 357,431 kilometers (222,097 miles) at 8:25
7/14 The Moon is at ascending node (longitude 125.9 degrees) at 2:52; the Moon is 1.1 degrees south-southwest of the bright open cluster M44 at 6:00; the Moon is 2.1 degrees north-northeast of Mercury at 23:00
7/15 The Moon is 1.7 degrees north-northeast of Regulus at 17:00
7/16 The Moon is 1.6 degrees north-northeast of Venus at 4:00
7/19 The Moon is 7.2 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 14:00; First Quarter Moon occurs at 19:52
7/20 The Lunar X, also known as the Werner or Purbach Cross, an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to begin at 6:15; asteroid 88 Thisbe (magnitude +9.7) is at opposition at 9:00; Mercury is at aphelion (0.4667 a.u. from the Sun) at 10:00; sunrise takes place on the isolated lunar mountain Mons Pico at 13:00
7/21 The Sun enters Cancer, at ecliptic longitude 118.25 degrees, at 1:00; the Moon is 4.2 degrees north-northeast of Jupiter at 3:00; sunrise takes place on the isolated lunar mountain Mons Piton at 4:21
7/23 The Moon is 8.9 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 7:00
7/24 Mercury (magnitude +1.5) is 7.6 degrees west of Regulus (magnitude +1.4) at 18:00
7/25 The Moon is 2.0 degrees north of Saturn at 6:00; Mercury is stationary in right ascension, with retrograde (westward) motion to commence, at 7:00
7/26 Mercury is stationary in longitude at 5:00; the equation of time equals -6.54 minutes at 6:00
7/27 Mars is at opposition (magnitude -2.8, angular diameter 24.3") at 5:00; the Moon is at apogee, subtending 29' 25" from a distance of 406,223 kilometers (252,415 miles) at 5:44; a total lunar eclipse begins its penumbral phase at 17:14:38; Full Moon, known as the Hay or Thunder Moon, occurs at 20:20; the instant of greatest lunar eclipse occurs at 20:21:45; the Moon is at the descending node (longitude 305.9 degrees) at 22:41
7/28 The Southern Delta Aquarid meteor shower (15 to 20 per hour) peaks at 9:00; the middle of the eclipse season, i.e., when the Sun is at the same longitude as the Moon’s ascending node (125.8 degrees), occurs at 23:00
7/30 A double Galilean satellite shadow transit (Io’s shadow precedes Europa’s) begins at 7:21
7/31 The Moon is 2.4 degrees south-southeast of Neptune at 7:00; Mars is at its closest approach to the Earth (0.385 a.u.) at 8:00
Friedrich Bessel 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. The Apollo 11 lunar module landed on the Moon on July 20, 1969. Fragments of Comet D/1993 F2 (Shoemaker-Levy) impacted Jupiter on July 16, 1994.
The peak of the Southern Delta Aquarid meteor shower on the morning of July 30th is compromised by moonlight. The radiant is located northwest of the first-magnitude star Fomalhaut (Alpha Piscis Austrini). Southern hemisphere observers are favored. Click on http://earthsky.org/...d-meteor-shower for further information. Other minor meteor showers with southern radiants occurring this month are the Alpha Capricornids, the Piscis Austrinids, and the Northern Delta Aquarids.
Information on Iridium flares and passes of the ISS, the Tiangong-2, the USAF’s X-37B, the HST, and other satellites can be found at http://www.heavens-above.com/
The Moon is 17.0 days old, is illuminated 93.9%, subtends 29.4 arc minutes, and is located in Capricornus on July 1st at 0:00 UT. The Moon is at its greatest northern declination of +20.6 degrees on July 12th and its greatest southern declination of -20.7 degrees on July 26th. Longitudinal libration is at a maximum of +7.5 degrees on July 20th and a minimum of -7.6 degrees on July 7th. Latitudinal libration is at a maximum of +6.8 degrees on July 8th and a minimum of -6.8 degrees on July 20th. New Moon takes place on July 13th. Large tides will occur afterwards. The Moon is at perigee on July 13th and at apogee on July 27th. A total lunar eclipse, the 38th of Saros 129, takes place on July 27th, with the penumbral eclipse starting at 17:14:48 UT and ending at 23:48:42 UT. Totality begins at 19:30:17 and ends at 21:13:14 UT, with the instant of greatest lunar eclipse occurring at 20:21:45. The eclipse is not visible from North America. The Moon occults Aldebaran from various parts of the world on July 10th. See http://www.lunar-occ...ota/iotandx.htm for information on this and other lunar occultations taking place in July. Visit http://saberdoesthes...does-the-stars/ for tips on spotting extreme crescent Moons. Click on https://www.calendar...endar/2018/july for a lunar phase calendar for this month. The times and dates for the lunar crater light rays predicted to occur in July are available at http://www.lunar-occ.../rays/rays.htm
The Sun is located in Gemini on July 1st. The Earth is farthest from the Sun on July 6th, when it is 3.3% more distant than it was at perihelion and 1.7% farther than its average distance. A partial solar eclipse visible from extreme southeastern Australia, the South Pacific Ocean, the South Indian Ocean, the Antarctic Ocean, and far northern Antarctica occurs on July 13th. This will be the 69th eclipse of Saros 71. Greatest eclipse takes place at 3:01:07 UT. The Sun enters Cancer on July 21st.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on July 1st: Mercury (-0.1 magnitude, 6.6", 61% illuminated, 1.02 a.u., Cancer), Venus (-4.1 magnitude, 15.7", 70% illuminated, 1.06 a.u., Leo), Mars (-2.2 magnitude, 20.9", 97% illuminated, 0.45 a.u., Capricornus), Jupiter (-2.3 magnitude, 41.4", 99% illuminated, 4.76 a.u., Libra), Saturn (+0.0 magnitude, 18.4", 100% illuminated, 9.05 a.u., Sagittarius), Uranus (+5.8 magnitude, 3.5", 100% illuminated, 20.01 a.u. on July 16th, Aries), Neptune (+7.8 magnitude, 2.3", 100% illuminated, 29.32 a.u. on July 16th, Aquarius), and Pluto (+14.2 magnitude, 0.1", 100% illuminated, 32.59 a.u. on July 16th, Sagittarius).
Mercury and Venus are located in the west, Mars in the southeast, Jupiter in the south, Saturn in the southeast during the evening. At midnight, Mars is in the southeast, Jupiter is in the southwest, Saturn is in the south, and Neptune is in the east. In the morning, Mars can be found in the southwest, Uranus in the southeast, and Neptune in the south.
Mercury undergoes a somewhat mediocre apparition for northern hemisphere observers this month. The speediest planet passes within one degree of M44 on July 3rd and July 4th. Mercury is at dichotomy on July 7th. Mercury enters Leo on July 14th. A thin crescent Moon passes within two degrees of the planet on that evening.
Venus brightens to a brilliant magnitude -4.3 by the end of July. It passes one degree north of Regulus on the night of July 9th. A three-day-old waxing crescent Moon passes within two degrees of the planet on the night of July 15th/July 16th.
Mars reaches opposition at 5:00 UT on July 27th, the best opposition since the historic 2003 opposition. At that time, it will rise at sunset, shine at magnitude -2.8, and subtend 24.3 arc seconds. Mars will be 57.6 million kilometers (35.8 million miles) or 32 light minutes from Earth and 25.5 degrees south of the celestial equator. As seen from the Eastern Hemisphere, a totally eclipsed Moon will pass some six degrees to the north of Mars at opposition. Closest approach to the Earth occurs on July 31st. Most unfortunately, a planet encircling/global dust storm is currently obscuring the surface features of the Red Planet. Articles on observing Mars can be found online at http://www.alpo-astr...h/2018_MARS.htm and on pages 22 through 27 of the July 2018 issue of Sky & Telescope. An article on observing the Martian satellites Phobos and Deimos appears on pages 52 and 53 of that same issue. Click on https://www.skyandte...watching-tools/ and https://www.calsky.c...gi/Planets/5/1? in order to use Martian surface feature simulators.
Jupiter drops in brightness by two tenths of a magnitude and in apparent size by more than three arc seconds this month. Jupiter is situated two degrees from the double star Zubenelgenubi (Alpha Librae) in western Libra when it resumes prograde or direct (eastern) motion on July 11th. The waxing gibbous Moon passes four degrees to the north of Jupiter on the night of July 20th. Information on Great Red Spot transit times and Galilean satellite events is available on pages 50 and 51 of the July 2018 issue of Sky & Telescope and online at http://www.skyandtel...watching-tools/ and https://www.projectp....com/jevent.htm
Saturn is 4.7 degrees due east of M20 (the Trifid Nebula) and four degrees southwest of the open cluster M25 as July begins. It lies 2.7 degrees east of M20, which is an unusual combination of an open cluster, an emission nebula, a reflection nebula, and a dark nebula, as the month ends. On the night of July 4th/July 5th, Saturn occults the tenth-magnitude star TYC 6277-323-1 (BD-22 4689) beginning around 4:10 UT (12:10 a.m. EDT). Tenth-magnitude Tethys will be a mere 10 arc seconds from the star at 1:45 UT (9:45 p.m. EDT). For more on this event, consult page 50 of the July 2018 issue of Sky & Telescope. In mid-July, Saturn’s rings span 41 arc seconds and are tilted some 26 degrees with respect to the Earth. The planet’s disk subtends 18.3 arc seconds at the equator. On July 25th, a waxing gibbous Moon passes two degrees north of the Ringed Planet. The faint Saturnian satellite Iapetus shines at eleventh magnitude and is positioned 1.7 arc minutes due north of Saturn on the night of July 1st. For further data on Saturn’s satellites, browse http://www.skyandtel...watching-tools/
Uranus can be found in southwestern Aries approximately twelve degrees south of the second-magnitude star Hamal (Alpha Arietis). A waning crescent Moon passes less than five degrees south-southeast of Uranus on July 7th. Visit http://bluewaterastr...anus_2018_1.pdf and http://www.nakedeyep....com/uranus.htm for finder charts.
Neptune is located in eastern Aquarius. The eighth planet is situated 0.9 degree west-southwest of the fourth-magnitude star Phi Aquarii at the start of the month. By the end of July, Neptune lies 1.4 degrees from that star. A waning gibbous Moon passes less than three degrees south-southeast of Neptune on July 4th and July 31st. Browse http://bluewaterastr...tune_2018_1.pdf and http://www.nakedeyep...com/neptune.htm for finder charts.
Finder charts for Uranus and Neptune are also available at https://www.skyandte...WEB_UrNep18.pdf
On the evening of July 3rd, Pluto passes 35 arc seconds west of the sixth-magnitude star 50 Sagittarii. The dwarf planet is at opposition on July 12th. Finder charts can be found on page 43 of the July 2018 issue of Astronomy (good for the first two weeks of the month), pages 48 and 49 of the July 2018 issue of Sky & Telescope, and on page 243 of the RASC Observer’s Handbook 2018.
A podcast on the planets this month can be heard at https://www.skyandte...cast-july-2018/
For more on the planets and how to locate them, browse http://www.nakedeyeplanets.com/
The periodic comet 21P/Giacobini-Zinner may shine at tenth magnitude as it travels northeastward from Cygnus into Cepheus. See http://cometchasing.skyhound.com/ and http://www.aerith.ne...t/future-n.html for additional information on comets visible this month.
Asteroid 4 Vesta decreases in brightness from magnitude +5.6 to magnitude +6.3 as it travels southwestward through Ophiuchus this month. It passes about one degree north of the sixth-magnitude star 52 Ophiuchi on June 7th. On July 14th, Vesta enters the dark nebula known as the Dark Horse or Prancing Horse Nebula. A finder chart can be found on page 48 of the June 2018 issue of Sky & Telescope. Asteroid 3 Juno passes less than three degrees south of Uranus on the morning of July 5th. A number of asteroids with magnitudes of +11.0 or brighter reach opposition this month including 88 Thisbe, 14 Irene, 26 Proserpina, 197 Ampella, 140 Siwa, and 144 Vibilia. Information on asteroid occultations taking place this month is available at http://www.asteroido.../2018_07_si.htm
Various events taking place within our solar system are discussed at http://www.bluewater...ed-4/index.html
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/
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.