April 24, 2021

AstroCal – May 2021


     The past several AstroCals, our poor companion seems to have gotten short shrift as the Full Moon has taken place very late in the last few months.  We will rectify that situation by starting this edition with the May Lunar events.  Not only will this month’s Full Moon take place late in the month (May 25 to be exact), it will be a so-called “Supermoon”.  Supermoons are those Full Moons that happen closest to perigee, or the closest the Moon comes to Earth.  This syzygy (the technical name for the same event) will mark the second closest Moon of the year when it will be 222,023 miles from Earth.  A brief total lunar eclipse will be visible in the early morning hours of May 26, but only for the western U.S. (the Moon will have already dropped below the horizon for those of us in the eastern part of the country).  More details and links about the eclipse can be found on Abrams Planetarium’s Extra Content Page .

     Hopping back to the beginning of the month, the Waning Quarter & Crescent Moon will dominate the SE sky in the 1 ¼ hours before sunrise.  The Young Crescent Moon will be visible with Venus in the WNW 40 minutes after sunset on May 12 with the First Quarter coming on May 19.

     Speaking of planets, Venus will be shining brightly at a magnitude of -4 (the smaller the number, the brighter the object) and will be easy to spot in the WNW in the hour after sunset all month long.  Venus is the third brightest natural object seen in our sky after the Sun and the Moon and is named for the Roman goddess of love and beauty.  Let us also not forget that the name can be remembered as the song title of hits by both Frankie Avalon (1963), Shocking Blue (1969), and Bananarama (1986), the later two being different versions of the same tune.

     Mercury will be in a favorable position to be seen just above Venus.  At the beginning of May, it will start at a bright -1.1 magnitude but it will rapidly fade to +1.5 by the 24th.  Mars will appear even dimmer at +1.6 to +1.7 but being higher in the sky, it should be easier to spot in dark sky locations.  The Abrams Sky Calendar provides the following detailed viewing instructions for this months ‘viewing challenge:  “Using binoculars, track Mars’ motion of 0.6 degrees per day as it passes by 3rd-mag. Stars in Gemini on Apr. 28 – May 2, May 9 and 23, and forms noteworthy configurations with brighter Pollux (+1.2) and Castor (+1.6) on May 15, 31, and June 7.”

     Jupiter, our nearest Gas Giant neighbor, will dominate the morning sky.  At the start of May, it will rise three hours ahead of the Sun in the eastern sky.  The rising time will increase to four hours ahead of sunrise by May 31.  As a bright morning star, Jupiter will increase in magnitude from -2.2 to -2.4 during May.  Saturn can also be viewed in the morning sky in the SE, slightly above and to the ‘right’ of Jupiter.  The Ringed Planet (at least the one ringed planet whose rings we can see from Earth with a moderate sized telescope) will be three mags fainter than Jupiter and will brighten slightly from +0.7 to +0.6 during the month.  

     A visit to the previously mentioned Extra Content Page at Abrams Planetarium will provide you with information about conjunctions of Jupiter and Saturn with background stars.  The site will also help you track J & S’s impending retrograde motions and notes about May’s rare events involving Jupiter’s moons and 3-D aspects of Saturn’s Rings.

 Compiled by Ken Raisanen of WOAS-FM – information provided by Abrams Planetarium Sky Calendar, Michigan State University.  More information can be found on the their website at or on Twitter at

Top Piece Video:  Venus by any other name . . .