Skywatch Line for Wednesday, September 29, and Thursday, September 30, 2021

This is Dudley Observatory’s Skywatch Line for Wednesday, September 29, and Thursday, September 30, written by Alan French.

The Sun sets at 6:40 P.M. on Wednesday and rises at 6:52 A.M. Thursday. Sunset Thursday is at 6:38 and the Sun will rise at 6:53 on Friday.

The Moon reached last quarter this past Tuesday night and is now headed toward new. It will reach new on Wednesday morning, October 6. The Moon rises at 11:55 P.M. Wednesday night and after midnight on Thursday, rising at 12:57 A.M. Friday morning.

On Thursday morning at 5:00 A.M., the waning crescent Moon, 37% illuminated, will be in the constellation Gemini, not far from the constellation’s brightest stars, Castor and Pollux. The Moon will be high in the east, with Pollux 3-degrees to its left and Castor a little over 6-degrees away to the upper left.

By Friday morning the Moon’s eastward motion among the stars will have it in Cancer. Now 28% illuminated the Moon will be just under four degrees from the famous Beehive Cluster, an open cluster of stars known since ancient times. It is easily seen by eye under dark, moonless skies, but binoculars will reveal it in spite of the competition of the Moon. Look for it to the lower right of the Moon, at about the 5 o’clock position. In a week, with the Moon out of the way, you try the Beehive Cluster by eye.

While the ISS (International Space Station) is brightest and most impressive when it passes high overhead, it’s easily visible when it’s lower in the sky. Wednesday and Thursday provide chances to watch it pass across the northern sky, and both passes will have the ISS move into the Earth’s shadow and fade from view..

On Wednesday night look for the ISS moving up from the northwestern horizon at 8:32 P.M. It moves slowly at first and is dimmed by the thick atmosphere near the horizon, so you may not spot it right away. By 8:34 it will be approaching the back of the Big Dipper’s bowl. It will pass through the Big Dipper and then below the Little Dipper. As it moves below Polaris, the North Star, it will move into the Earth’s shadow and fade from view. How far can you follow it before it completely vanishes from view?

Thursday night’s pass will cross more of the northern sky before moving into the Earth’s shadow. Look for the ISS coming up from the northwestern horizon at 7:45 P.M. Passing a little lower in the sky than Wednesday, it may take longer to first spot the space station. At 7:47 is will be passing just below the Big Dipper’s bowl. Just after 7:48 it will be due north and passing below Polaris. At 7:49 it will pass below the familiar “W” pattern of stars marking the constellation Cassiopeia, the Queen. Just after 7:50, as it moves toward the horizon, it will move into the Earth’s shadow and fade from view.

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