CSTA Classroom Science

California Skies, May, June, and July 2021

By Robert C. Victor and Robert D. Miller

The May 2021 Sky Calendar, depicting gatherings of Moon, planets, and bright stars at dusk and dawn, and a detailed map of the evening sky are now available for free download here.

The calendar and map may be reprinted for free distribution to teachers and students.

Events visible on May evenings, illustrated on the calendar are:

  • This year’s best appearance of Mercury at dusk, lasting through the first three weeks of May;
  • Mars moving against the background of Gemini and forming striking configurations with the “Twin” stars Pollux and Castor, such as an isosceles triangle on May 15;
  • Venus just getting started as an evening “star, ”very low in WNW;
  • The Moon’s journey past planets and bright zodiacal stars;
  • And the annual disappearance of four bright winter stars, Rigel, Aldebaran, Sirius, and Betelgeuse, below the western horizon.

Noteworthy events for all three months May through July, both evening and morning, are described in detail in the Sky Calendar extra content page.

Outstanding events for early risers on May mornings are:

Jupiter and Saturn 15°-18° apart in the southeast before dawn brightens. Telescopes give fine views of Jupiter’s four Galilean satellites and Saturn’s rings. Of the three cases mentioned  when one of Jupiter’s moons eclipses another, only one, Friday, May 28, offers an event visible from California, a total eclipse of Io by Ganymede.

The prime event in May is the eclipse of the Moon in the predawn hours of Wednesday, May 26. The Moon’s encounter with the dark core of Earth’s shadow begins at the start of partial eclipse at 2:45 a.m. PDT. The Moon is half in shadow by 3:18 a.m., and in total eclipse for only 14.5 minutes, from 4:11.5 a.m. until 4:26 a.m. PDT, low in the southwest. California offers the best view of the total lunar eclipse in the contiguous 48 states. Within the U.S., only Hawaii offers a better view.

Just 15 days after the total lunar eclipse, there’s a solar eclipse on the morning of Thursday, June 10, but nothing of that event will be visible from California.

The Sky Calendar extra content page concludes with a summary of planet and bright star visibility and sky events at dusk and dawn for all three months, accompanied by evening and morning twilight sky charts, kindly provided by Robert D. Miller.

Here’s wishing you clear skies! Stay safe and healthy, and we’ll look forward to sky watching sessions in the fall of 2021, when Venus, Saturn, and Jupiter will all put on a spectacular show in the early evening sky.



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Written by Robert C. Victor

Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs, CA. Robert is a member of CASE.


Written By Robert D. Miller

Miller did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

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