Skywatch Line for Friday, October 15, through Sunday, October 17, 2021

This is Dudley Observatory’s Skywatch Line for Friday, October 15, through Sunday, October 17, written by Sam Salem.

On Friday, Sun rises at 7:09am and sets at 6:12pm; Moon sets at 1:30am and rises at 4:29pm. The waxing Moon sweeps past bright Jupiter and fainter Saturn in the evening sky on Friday. Jupiter appears brighter than any star. Saturn appears fainter and more golden in color than Jupiter. Extend your arm and make a fist. Saturn is the brightest object within one fist-width of Jupiter to the right. Saturn is brighter than the nearby bright star Fomalhaut in constellation in the constellation Piscis Austrinus, the southern Fish.

On Sunday night, the terminator on the waxing gibbous Moon will fall west of Sinus Iridum, the Bay of Rainbows. The circular, 249-kilometre diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its east, forming a rounded “handle” on the western edge of that mare. The “golden handle” effect is produced when sunlight strikes the prominent Montes Jura mountain range surrounding Sinus Iridum on the north and west. In a telescope, Sinus Iridum is almost craterless but hosts a set of northeast-oriented wrinkle ridges that are revealed at this Moon phase.

In the southwestern sky on the evenings around Saturday, the orbital motion of the bright planet Venus will carry it closely above the bright reddish star Antares, which marks the heart of Scorpius. At closest approach on Saturday, they’ll share the field of view in the eyepiece of a telescope at low magnification. If you have trouble seeing Antares beside 150 times brighter Venus, try hiding Venus just outside of your field of view. Venus stays close to Antares for the next two days. Watch their orientation change.

This is the time of year when, soon after nightfall, W-shaped constellation Cassiopeia stands on end halfway up the northeastern sky. Off to its left in the north, the dim Little Dipper extends directly leftward from Polaris. Cassiopeia is well placed high in the northeast together with constellations of Perseus and Auriga, the Charioteer, visible in the east.

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