This is the Dudley Observatory Skywatch Line for Monday and Tuesday, October 19th and 20th written by Joe Slomka.
The Sun sets at 6:07 PM; night falls at 7:41. Dawn breaks at 5:40 AM and ends with sunrise at 7:14.
The six-day-old Moon brightens the evening sky. Monday’s Moon, in Sagittarius, blazes at minus 9.3 magnitude and appears about forty percent illuminated. Tuesday, the First Quarter Moon, also in Sagittarius, appears half illuminated. On both days, the Moon sets after 6 PM.
Saturn, the sole easy planet, has migrated from Libra to Scorpius. At 0.6 magnitude, it shines quite low on the western horizon. Earth’s turbulent atmosphere makes viewing the planet difficult by smearing details of the beautiful ring system. Saturn sets before 8 PM.
Nightfall contains three dim, distant solar system bodies. Neptune resides in Aquarius; but the nearby Moon may make observation difficult. Uranus, in Pisces, is further away and needs detailed charts to find it. Asteroid 4Vesta is in Cetus, about one-and-a-half degrees below the star Iota Ceti. All four require finder charts available from astronomy magazines, websites and apps. Neptune sets about 3 AM and Vesta follows at 4:43 AM. Uranus is up all night.
Dawn presents four bright planets for our enjoyment. Venus rises first at 3:18 AM, and, before sunrise, blazes between Leo’s hind legs. High-powered binocular or telescope views show Venus about half illuminated. Jupiter, less brilliant than Venus, lies about four-and-a-half degrees below Venus. Much dimmer Mars is about one-and-a-half degrees below Venus. Notice their locations, the three switch positions in the coming days.
Mercury brings up the rear by rising at 5:43 AM in Virgo. It is moderately low in the eastern sky, but its minus 0.8 magnitude should permit views despite the Sun’s glare. Do not confuse the bright star Arcturus for Mercury. Under high powers, Mercury appears about three-quarters illuminated.
When the Moon is out of the way, observers are able to study dim or obscure objects. Several dim but lovely constellations are sandwiched between brighter Pegasus, Aquarius and Cygnus. One of these is Delphinus, the Dolphin. It looks like a diamond with a tail and replicates a dolphin leaping out of the water. It is found midway between Pegasus’ and Cygnus’ noses.
There are two Greek myths about Delphinus. One states that covetous crewmen threatened Arion, a rich poet, while he was traveling. When he was flung overboard into the sea, he was rescued by a dolphin, which safely transported the poet to the Greek coast.
Most star names are derived from legends or description. Delphinus is an exception. Its two brightest stars, Alpha and Beta, were the subjects of a practical joke. An Italian astronomer, Niccolo Cacciatore, decided to give them proper names. In Latin, his name was “Nicolaus Venator”. He assigned the name “Sualocin” to Alpha, and “Rotanev” to Beta. These names are “Nicolaus Venator” spelled backwards. The practical joke stuck! Today, these are accepted proper names for Alpha and Beta Delphini.