This is the Skywatch Line for Monday and Tuesday, August 20th and 21st.
The Sun sets at 7:49 PM; night falls at 9:35. Dawn breaks at 4:22 AM and ends with sunrise at 6:08.
The evening planetary parade continues. Venus, in Virgo, blazes with minus 4th magnitude low in the western sky. Our binoculars or telescope reveals it to be about 47% lit, but 25 arc-seconds in size. It sets at 9:22 PM.
Jupiter is moderately low in the southwestern sky, blazes at minus 2nd magnitude and is a large 35 arc-seconds in size. It continues to accompany Libra’s bright star Zubenelgenubi. By twilight’s end, it hovers about 13º above the horizon and sets at 10:55 PM.
Saturn is also moderately low in southern Sagittarius. It glows with zero magnitude and appears about 17 arc-seconds in size. Monday night it appears about 4º to the Moon’s lower left; Tuesday night finds it only 2º away from the Ringed Planet. Saturn and its rings are best observed at 9:10 PM; it sets at 1:42 AM.
Mars brings up the rear, in Capricornus. Moderately low at Civil Dusk, it is best observed at 11:07 PM, when it is highest. Mars outshines Jupiter, but appears smaller with only 22 arc-seconds in size. The dust storm continues, but is showing some signs of moderating. It sets at 3:21 AM.
As mentioned, the Moon inhabits Sagittarius both nights. It blazes with minus 10th magnitude and appears 75% illuminated on Monday night; Tuesday finds it brighter and 83% lit. Its glare will degrade views of Saturn and its rings for those nights. The Moon is highest at 8:51 PM on Monday, and at 9:40 Tuesday. It sets at 1:40 AM on Tuesday and at 2:26 AM on Wednesday.
Neptune rises, in Aquarius, near the star Phi Aquarii, during twilight. It shines with 7th magnitude and appears a tiny 2.4 arc-seconds in size. It is best situated at 2:35 AM. Uranus, in Aries, rose at 10:08 PM and shines with 5th magnitude and appears slightly larger. It is ideally viewed at 4:58 AM. Both of these distant members of our Solar System require detailed finder charts from astronomical media.
Mercury makes a Dawn appearance. Rising in Cancer at 4:49 AM, it shines with 1st magnitude, appears about 22% lit, and is about 8 arc-seconds in size. However, at 8º altitude, early observers may need the assistance of binoculars in finding the elusive planet amid the brightening sky.
Ancient peoples saw the sky as the realm of the gods and told stories about their constellations. By midnight, all the constellations that make up the Andromeda saga are visible. We previously mentioned Cassiopeia and Cepheus. Cassiopeia angered some gods and Ethiopia was subjected to severe calamities. An oracle told Cepheus that disasters would end if he chained Andromeda to a seaside rock to be eaten by the sea monster Cetus. Perseus was returning from a mission to kill the Medusa, a woman so hideous that her visage turned people to stone. One version of the myth has Perseus returning by his pet horse Pegasus. He hears Andromeda’s cry for help. The parents, nearby, promise her hand in marriage if he saves her. He kills Cetus and frees Andromeda. “W” shaped Cassiopeia and Cepheus, shaped like a stick drawing of a house, are visible overhead. Pegasus, the flying horse, is a Great Square high in the eastern sky, flying upside down; his neck begins at the lower right star of the square. Andromeda’s chains flow from the square’s upper left star and continue eastward. The famous Andromeda Galaxy lies above the upper chain and is visible to naked eyes in rural skies. Perseus appears to the east of Pegasus, resembling a stick drawing of a man with one long and one short leg. The brightest star in the short leg is Algol, the “Demon Star.” It represents the evil eye of the Medusa. Cetus lies beneath Pegasus and Pisces. It is a dim constellation low on the horizon for our latitude.