May 2020 Celestial Calendar

May 1, 2020
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May Celestial Calendar by Dave Mitsky

All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)

5/1 Today is May Day or Beltane, a cross-quarter day; Mercury is 0.3 degrees southeast of Uranus at 5:00
5/2 The Moon is 4.0 degrees north-northeast of the first-magnitude star Regulus (Alpha Leonis) at 6:00
5/4 Venus is at its northernmost declination (27.8 degrees) at 0:00; Mercury is in superior conjunction with the Sun (1.325 astronomical units from the Earth, latitude -0.45 degrees) at 22:00
5/5 The peak of the Eta Aquarid meteor shower (a zenithal hourly rate of 20 per hour for northern hemisphere observers) occurs at 5:00; Mercury is at the ascending node through the ecliptic plane at 12:00; the Moon is 6.7 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 23:00
5/6 The Moon is at perigee, subtending 33' 13'' from a distance of 359,654 kilometers (223,478 miles), at 3:03
5/7 Full Moon, known as the Milk or Planting Moon, occurs at 10:45
5/9 The Moon is 6.3 degrees north-northeast of the first-magnitude star Antares (Alpha Scorpii) at 1:00
5/10 Mercury is at perihelion (0.3075 astronomical units from the Sun) at 4:00; the Moon is at the descending node (longitude 269.7 degrees) at 9:00
5/11 Saturn stationary at 9:00; asteroid 2 Pallas is stationary at 11:00
5/12 Mercury is 2.9 degrees southeast of the third-magnitude star Alcyone (Eta Tauri) in the bright open cluster M45 (the Pleiades or Subaru) in Taurus at 4:00; the Moon is 2.2 degrees south of Jupiter at 11:00; the Moon, Jupiter, and Saturn all lie within a circle with a diameter 4.7 degrees at 14:00; the Moon is 2.7 degrees southeast of Saturn at 20:00
5/13 Venus is stationary at 10:00; the equation of time is at a maximum of 3.65 minutes at 15:00; the Sun enters Taurus, at longitude 53.5 degrees on the ecliptic, at 20:00
5/14 Last Quarter Moon occurs at 14:03; Jupiter is stationary at 18:00
5/15 The Moon is 2.6 degrees southeast of Mars at 5:00
5/16 The Curtiss Cross, an X-shaped clair-obscure illumination effect located between the craters Parry and Gambart, is predicted to be visible at 3:52; Mars and Jupiter are at heliocentric conjunction (longitude 287.4 degrees) at 15:00; Mercury is 7.2 degrees north of the first-magnitude star Aldebaran (Alpha Tauri) at 16:00; the Moon is 4.1 degrees southeast of Neptune at 19:00
5/18 Jupiter is 4.7 degrees west-southwest of Saturn, a quasi-conjunction, at 6:00; the Moon is at apogee, subtending 29' 28'' from a distance of 405,583 kilometers (252,018 miles), at 7:45
5/20 Mercury is at its northernmost latitude from the ecliptic plane (7.0 degrees) at 9:00; the Sun reaches a longitude of 60 degrees at 14:00; the Moon is 3.6 degrees southeast of Uranus at 19:00
5/22 Mercury is 0.9 degree southeast of Venus at 10:00; the Moon is 6.6 degrees southeast of the bright open cluster M45 at 16:00; New Moon (lunation 1205) occurs at 17:39
5/23 The Moon is 3.7 degrees north of Aldebaran at 9:00
5/24 The Moon is 3.6 degrees southeast of Venus at 5:00; the Moon, Mercury, and Venus all lie within a circle with a diameter of 4.4 degrees at 6:00; the Moon is 2.8 degrees southeast of Mercury at 13:00; the young crescent Moon is 0.6 degrees north of asteroid 4 Vesta, with an occultation occurring in the northern Middle East, western Russia, most of Europe, Greenland, the northern Caribbean, and most of North America, at 15:00; the Moon is at the ascending node (longitude 89.2 degrees) at 22:00
5/25 The Moon is 0.7 degree southeast of the bright open cluster M35 in Gemini at 4:00
5/26 The Moon is 8.2 degrees south of the first-magnitude star Castor (Alpha Geminorum) at 15:00; the Moon is 4.5 degrees south of the first-magnitude star Pollux (Beta Geminorum) at 20:00
5/27 Mercury is at its northernmost declination (25.7 degrees) at 5:00; asteroid 3 Juno is stationary at 14:00; the Moon is 2.0 degrees north-northeast of M44 (the Beehive Cluster or Praesepe) in Cancer at 21:00
5/28 A double Galilean shadow transit (Europa’s shadow follows Ganymede’s) begins at 8:48
5/29 The Moon is 4.1 degrees north-northeast of Regulus at 12:00; the Lunar X (also known as the Werner or Purbach Cross), an X-shaped clair-obscure illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to be fully formed at 14:10
5/30 First Quarter moon occurs at 3:30

Nicolas Lacaille (1713-1762), Otto Wilhelm Struve (1819-1905), Joseph Lockyer (1836-1920), Williamina Fleming (1857-1911), and Frank Drake (1930) were born this month.

The first recorded perihelion passage of Comet Halley (1P/Halley) occurred on May 25, 240 BC. Thales of Miletus accurately predicted a solar eclipse on May 28, 585 BC. The German astronomers Gottfried and Maria Magarethe Kirch discovered the bright globular cluster M5 on May 5, 1702. On May 1, 1759, the English amateur astronomers John Bevis and Nicholas Munckley observed Comet Halley on its first predicted return. The French astronomer Charles Messier discovered the globular cluster M3 on May 3, 1764 and the globular cluster M10 on May 29, 1764. The Italian astronomer Annibale de Gasparis discovered asteroid 11 Parthenope on May 11, 1850. Asteroid 14 Irene was discovered on May 19, 1851 by the English astronomer John Russell Hind. The German astronomer Robert Luther discovered asteroid 26 Proserpina on May 6, 1853. The Australian astronomer John Tebbutt discovered the Great Comet of 1861 on May 13. The English astronomer Norman Pogson discovered asteroid 80 Sappho on May 2, 1864. Norman Pogson discovered asteroid 87 Sylvia on May 16, 1866. The 40-inch Clark refractor at the Yerkes Observatory saw first light on May 21, 1897. The Griffith Observatory opened to the public on May 14, 1935. Nereid, Neptune’s third-largest satellite, was discovered on May 1, 1949 by the Dutch-American astronomer Gerard Kuiper.

The broad peak of the Eta Aquarid meteor shower is severely affected by a 91%-illuminated waxing gibbous Moon this year. Eta Aquarid meteors are debris from the famous periodic comet 1P/Halley. The radiant is located close to the Water Jug asterism in Aquarius. Southern hemisphere observers are favored. See and page 50 of the May 2020 issue of Sky & Telescope for additional information on the Eta Aquarids.

Information on passes of the ISS, the USAF’s X-37B, the HST, Starlink, and other satellites can be found at

The Moon is 7.7 days old, is illuminated 49.9%, subtends 32.1 arc minutes, and is located in Cancer on May 1st at 0:00 UT. The Moon is at its greatest northern declination on May 26th (+24.0 degrees). The Moon is at its greatest its greatest southern declination on May 11th (-24.0 degrees). Longitudinal libration is at maximum (+6.9 degrees) on May 12th and at minimum (-5.9 degrees) on May 27th. Latitudinal libration is at maximum (+6.7 degrees) on May 18th and at minimum (-6.6 degrees) on May 4th. The Moon is at perigee (distance 56.39 Earth-radii) on May 6th and at apogee (distance 63.59 Earth-radii) on May 18th. New Moon occurs on May 22nd. The Moon occults asteroid 4 Vesta on May 24th from certain parts of the world. Consult for more on lunar occultations. Consult for information on occultation events. Visit for tips on spotting extreme crescent Moons and for Full Moon data. Consult or download for current information on the Moon. See for a lunar phase and libration calculator and for the Lunar Reconnaissance Orbiter Camera (LROC) Quickmap. Click on 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

The Sun is located in Aries on May 1st. It enters Taurus on May 13th.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on May 1st: Mercury (magnitude -1.8, 5.1", 98% illuminated, 1.33 a.u., Aries), Venus (magnitude -4.7, 38.9", 25% illuminated, 0.43 a.u., Taurus), Mars (magnitude +0.4, 7.6", 86% illuminated, 1.23 a.u., Capricornus), Jupiter (magnitude -2.3, 40.7", 99% illuminated, 4.84 a.u., Sagittarius), Saturn (magnitude +0.6, 16.9", 100% illuminated, 9.81 a.u., Capricornus), Uranus on May 16th (magnitude +5.9, 3.4", 100% illuminated, 20.76 a.u., Aries), Neptune on May 16th (magnitude +7.9, 2.3", 100% illuminated, 30.34 a.u., Aquarius), and Pluto on May 16th (magnitude +14.3, 0.1", 100% illuminated, 32.74 a.u., Sagittarius).

In the evening, Mercury and Venus are in the northwest. Mars can be seen in the southeast, Jupiter and Saturn in the south, and Uranus and Neptune in the east at dawn.

The Moon, Jupiter, and Saturn lie within a circle with a diameter 4.7 degrees on May 12th. The Moon, Mercury, and Venus lie within a circle with a diameter of 4.4 degrees on May 24th.

Mercury is in superior conjunction on May 4th but can be seen low in west-northwest during evening twilight around May 11th. It is at perihelion on the previous day. Mercury passes less than a degree south of Venus on May 22nd. The two inner planets lie near the second-magnitude star El Nath (Beta Tauri). A very thin crescent Moon passes three degrees to the south of Mercury on May 24th.

Venus shines at magnitude -4.7 as May begins. Over the course of the month, its apparent diameter increases from 38.9 to 57.4 arc seconds while it decreases in illumination from 25 to 6%. On May 1st, Venus is positioned 23 degrees above the western horizon. As May progresses, Venus descends sunward. Venus begins to decrease in brightness after May 10th, ending the month at magnitude -4.4. It is stationary on May 13th and then begins retrograde motion. Venus enters Gemini during the second half of May. A young Moon passes four degrees south of Venus on May 24th. By May 31st, Venus is only three degrees in altitude at sunset.

Mars brightens from magnitude +0.4 to magnitude 0.0 and increases in apparent size from 7.6 to 9.2 arc seconds this month. Mars lies approximately one degree north-northwest of the fourth-magnitude star Gamma Capricorni on May 1st. The Red Planet departs Capricornus and enters Aquarius on May 9th. A waning crescent Moon passes three degrees south of Mars on May 15th. Mars and Jupiter are at heliocentric conjunction on May 16th. An article on observing the Mountains of Mitchel appears on pages 52 and 53 of the May 2020 issue of Sky & Telescope.

During May, Jupiter grows in apparent diameter from 40.7 to 44.6 arc seconds and brightens to magnitude -2.6. It rises around 2:00 a.m. local time on May 1st. The waning gibbous Moon passes two degrees to the south of Jupiter and Saturn on May 12th. Jupiter begins retrograde motion on May 14th. Jupiter is 4.7 degrees west-southwest of Saturn on May 18th. The gap between the two gas giants remains less than five degrees for the entire month. A shadow transit by Callisto begins at 2:30 a.m. EDT on the morning of May 3rd. Ganymede reappears from eclipse at 4:02 a.m. EDT and is occulted by Jupiter at 5:52 a.m. EDT. On the morning of May 21st, as Ganymede and the shadow of Europa are transiting the planet, they are joined by Europa at 5:23 a.m. EDT. Europa’s shadow joins Ganymede’s shadow at 4:48 a.m. EDT on the morning of May 28th. Browse or in order to determine transit times of Jupiter’s central meridian by the GRS. GRS transit information also appears on pages 50 and 51 of the May 2020 issue of Sky & Telescope. Data on the Galilean satellite events is available on page 51 of the May 20 issue of Sky & Telescope and online at and

Saturn shines at magnitude +0.4 and has an apparent equatorial diameter of almost 18 arc seconds. Saturn’s rings subtend about 37 arc seconds and are inclined by about 21 degrees. Saturn begins to retrograde on May 11th. Titan, which is Saturn’s brightest satellite at magnitude +8.6, is located south of the planet on May 5th and May 21st and north of it on May 13th and May 29th. Saturn’s peculiar satellite Iapetus shines faintly at eleventh magnitude when it passes 48 arc seconds south of the planet on May 11th. On May 31st, Iapetus brightens somewhat to magnitude +10.5 and is located nine arc minutes due west of Saturn as it reaches greatest western elongation. For further information on Saturn’s satellites, browse

Uranus can be seen once again during morning twilight during the last week of May. On May 20th, the waning crescent Moon passes four degrees southeast of Uranus.

Neptune lies three degrees east of the fourth-magnitude star Phi Aquarii in eastern Aquarius this month. The waning crescent Moon passes four degrees southeast of Neptune on May 16th. Neptune reaches an altitude of just 15 degrees in the east-southeastern morning sky in late May.

Pluto lies in northeastern Sagittarius some 2.1 degrees to the west of Jupiter and transits the meridian before dawn.

The promising comet C/2019 Y4 (ATLAS) has fragmented. Comet C/2017 T2 (PanSTARRS) passes southeastward through Camelopardalis and Ursa Major in May. A finder chart can be found on page 48 of the May 2020 issue of Sky & Telescope. Comet C/2020 F8 (SWAN) is moving rapidly northward and may reach a peak brightness of magnitude +3.5 between May 15th and May 23rd, as it travels from Triangulum into Perseus. Another comet that may be worth observing is comet. See for an article that discusses these comets and provides finder charts. Visit and for additional information on comets visible this month.

Two inner belt asteroids shine at tenth magnitude travel through Virgo this month. Asteroid 23 Thalia heads southwestward as asteroid 40 Harmonia travels northwestward. Both asteroids lie to the west of the fourth-magnitude star Iota Virginis. Information on asteroid occultations taking place this month is available at

For more on the planets and how to locate them, browse

A wealth of current information on solar system celestial bodies is posted at and

Information on the celestial events transpiring each week can be found at and and

Free star maps for May can be downloaded at and

Data on current supernovae can be found at

Finder charts for the Messier objects and other deep-sky objects are posted at and and

Telrad finder charts for the Messier Catalog and the SAC’s 110 Best of the
NGC are posted at and respectively.

Information pertaining to observing some of the more prominent Messier galaxies can be found at

Stellarium and Cartes du Ciel are two excellent freeware planetarium programs that are available at and

Deep-sky object list generators can be found at and and

Freeware sky atlases can be downloaded at and

Eighty binary and multiple stars for May: 1 Bootis, Struve 1782, Tau Bootis, Struve 1785, Struve 1812 (Bootes); 2 Canum Venaticorum, Struve 1624, Struve 1632, Struve 1642, Struve 1645, 7 Canum Venaticorum, Alpha Canum Venaticorum (Cor Caroli), h2639, Struve 1723, 17 Canum Venaticorum, Otto Struve 261, Struve 1730, Struve 1555, h1234, 25 Canum Venaticorum, Struve 1769, Struve 1783, h1244 (Canes Venatici); 2 Comae Berenices, Struve 1615, Otto Struve 245, Struve 1633, 12 Comae Berenices, Struve 1639, 24 Comae Berenices, Otto Struve 253, Struve 1678, 30 Comae Berenices, Struve 1684, Struve 1685, 35 Comae Berenices, Burnham 112, h220, Struve 1722, Beta Comae Berenices, Burnham 800, Otto Struve 266, Struve 1748 (Coma Berenices); h4481, h4489, Struve 1604, Delta Corvi, Burnham 28, h1218, Struve 1669 (Corvus); H N 69, h4556 (Hydra); Otto Struve 244, Struve 1600, Struve 1695, Zeta Ursae Majoris (Mizar), Struve 1770, Struve 1795, Struve 1831 (Ursa Major); Struve 1616, Struve 1627, 17 Virginis, Struve 1648, Struve 1658, Struve 1677, Struve 1682, Struve 1689, Struve 1690, 44 Virginis, Struve 1719, Theta Virginis, 54 Virginis, Struve 1738, Struve 1740, Struve 1751, 81 Virginis, Struve 1764, Struve 1775, 84 Virginis, Struve 1788 (Virgo)

Notable carbon star for May: SS Virginis

One hundred and sixty-five deep-sky objects for May: NGC 5248 (Bootes); M3, M51, M63, M94, M106, NGC 4111, NGC 4138, NGC 4143, NGC 4151, NGC 4214, NGC 4217, NGC 4244, NGC 4346, NGC 4369, NGC 4449, NGC 4485, NGC 4490, NGC 4618, NGC 4631, NGC 4656, NGC 4868, NGC 5005, NGC 5033, NGC 5297, NGC 5353, NGC 5354, Up 1 (Canes Venatici); Mel 111, M53, M64, M85, M88, M91, M98, M99, M100, NGC 4064, NGC 4150, NGC 4203, NGC 4212, NGC 4251, NGC 4274, NGC 4278, NGC 4293, NGC 4298, NGC 4302, NGC 4314, NGC 4350, NGC 4414, NGC 4419, NGC 4448, NGC 4450, NGC 4459, NGC 4473, NGC 4474, NGC 4494, NGC 4559, NGC 4565, NGC 4651, NGC 4689, NGC 4710, NGC 4725, NGC 4874, NGC 5053 (Coma Berenices); NGC 4027, NGC 4038-9, NGC 4361 (Corvus); M68, M83, NGC 4105, NGC 4106, NGC 5061, NGC 5101, NGC 5135 (Hydra); M40, NGC 4036, NGC 4041, NGC 4051, NGC 4062, NGC 4085, NGC 4088, NGC 4096, NGC 4100, NGC 4144, NGC 4157, NGC 4605, NGC 5308, NGC 5322 (Ursa Major); M49, M58, M59, M60, M61, M84, M86, M87, M89, M90, M104, NGC 4030, NGC 4073, NGC 4168, NGC 4179, NGC 4206, NGC 4215, NGC 4216, NGC 4224, NGC 4235, NGC 4260, NGC 4261, NGC 4267, NGC 4281, NGC 4339, NGC 4343, NGC 4365, NGC 4371, NGC 4378, NGC 4380, NGC 4387, NGC 4388, NGC 4402, NGC 4429, NGC 4435, NGC 4438, NGC 4517, NGC 4526, NGC 4535, NGC 4536, NGC 4546, NGC 4550, NGC 4551, NGC 4567, NGC 4568, NGC 4570, NGC 4593, NGC 4596, NGC 4636, NGC 4638, NGC 4639, NGC 4643, NGC 4654, NGC 4666, NGC 4697, NGC 4698, NGC 4699, NGC 4753, NGC 4754, NGC 4760, NGC 4762, NGC 4866, NGC 4900, NGC 4958, NGC 5044, NGC 5054, NGC 5068, NGC 5077, NGC 5084, NGC 5087, NGC 5147, NGC 5170, NGC 5247, NGC 5363, NGC 5364 (Virgo)

Top ten deep-sky objects for May: M3, M51, M63, M64, M83, M87, M104, M106, NGC 4449, NGC 4565

Top ten deep-sky binocular objects for May: M3, M51, M63, M64, M84, M86, M87, M104, M106, Mel 111

Challenge deep-sky object for May: 3C 273 (Virgo)

The objects listed above are located between 12:00 and 14:00 hours of right ascension.
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