July 27, 2023

AstroCal – August 2023

AstroCal – August 2023


     Cue the Marcels (as in the song Blue Moon) because August will be a two Full Moon month.  By the classic definition, the second Full Moon in a calendar month is called a Blue Moon.  Both of the August Full Moons will also be what are known as Super Moons so named when the Moon is closer to the Earth and appears larger than an average Full Moon.  This was a little confusing to me because I could not wrap my mind around how the Moon could be closer to the Earth twice in a month because with an elliptical orbit, it can only be closest to the Earth at one point in this orbit.  It turns out, there is a little more to the story of how Super Moons are identified.

     The first Super Moon will take place on August 1 when the moon is at perigee, or the closest its elliptical orbit will bring it to the Earth.   This fits the traditional idea of the Moon appearing larger when it is closer to the Earth.  Oddly enough, the Moon will be at apogee, or its farthest point from the Earth when it is again full on August 31.  How can it be a Supermoon if it is now farther from the Earth than it was on August 1?  Super Moons are also defined by the distance between the center of the Moon and the Earth.   Any time the Full Moon occurs when its center is less than 224,000 miles from the center of the Earth, it is called a Supermoon. 

      This means the August 31 Full Moon will not only be a Blue Moon (the name given to the second Full Moon in any given month), it will be a Super Blue Moon because its distance will be within this range.  This August 1 Full Moon is also known as the Sturgeon Moon.

     The Last Quarter Moon will take place on August 8 followed by the New Moon on August 16.  The First Quarter Moon will fall on August 24 and the previously mentioned Super Blue Moon will happen on August 31.  Look for an occultation of the star Antares, the Eye of Scorpius by the First Quarter Moon about one hour after sunset on the 24th.  With the Perseid meteor shower peaking in the early morning hours of August 13, the New Moon will offer excellent dark sky viewing.  It is not uncommon to see increased meteor activity a day before and the day after the August 13 peak.

     Shining at magnitude -2.3, Jupiter continues to dominate the morning skies even in areas with a good deal of light pollution.  It will be joined by Saturn later in the month.  Shining at +0.7, Saturn is a little more difficult to locate  but finding it is a bit easier if one looks just to the left of the Full Moon on August 2.  Saturn will reach opposition (when it will be directly opposite the Sun when viewed from Earth) making it visible in the east at sunset.  This positioning means it will be visible all night long as it crosses to the western sky before sunrise.  This month will also see a plane crossing of the Ringed Planet which happens approximately every 15 years.  This event takes place when the Rings of Saturn are viewed ‘edge on’ and is a prime time for astronomers to search for undiscovered moons.

     The evening planets include Mercury and Mars low in the western sky.  Mercury will be so low to the horizon it will be very difficult to observe.  Look for the Red Planet due west, just above the horizon 40 minutes after sunset.

     Our August historical event also involves Mars.  On August 11, 1877 Asaph Hall was working at the U.S. Naval Observatory when he discovered the Martian moon Diemos.  This is the smaller of the planet’s two tiny moons whose irregular shape has led some to describe them as ‘potato moons’.  Hall was becoming frustrated searching for any other Martian moons.  With his wife Angelina’s encouragement, he continued his observations and found Diemos’s larger companion Phobos six days later on August 17.

  Compiled by Ken Raisanen of WOAS-FM – information provided by Abrams Planetarium Sky Calendar, Michigan State University.  More information and subscription information can be found on their website at or on Twitter at  Yearly subscriptions cost $12 and can be started anytime.


Top Piece Video:  Okay, I could not find a live clip of the Marcels – so how about Sha Na Na’s pepped up version of Blue Moon?