Skywatch Line for Wednesday and Thursday, September 11 and 12, 2024, written by Alan French
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, September 11 and 12, 2024, written by Alan French.
The Sun rises at 6:31 A.M. on Wednesday and sets at 7:11 P.M. On Thursday it rises at 6:32 and sets at 7:09. This Thursday has 19 minutes, 54 seconds less daylight than last Thursday.
The Moon reached first quarter early Wednesday morning. The nights around first quarter are ideal for exploring the Moon with a telescope, and even a modest telescope will show a wealth of detail.
On Wednesday at 8:00 P.M., during evening twilight, the Moon will be 58% in sunlight and 17 degrees above the horizon toward the south. Lunar details will be most obvious along the lunar terminator, the line separating night and day. Here shadows are long and details stand out in bold relief. This is now the sunrise line, and it is fun to watch just into the darkness as new mountain peaks and crater rims gradually catch the light of the rising Sun. Also look for the sunlight slowly marching across and illuminating crater floors near the terminator.
At 8:00 P.M. Thursday night the Moon will be approaching due south and will be 18 degrees above the horizon. Its visible face will be 68% in sunlight.
On Wednesday night there will be an early, low pass of the ISS across the southeastern sky. Look for the ISS coming up from the south southwestern horizon at 8:01 P.M. At 8:02 it will be approaching the Moon and at 8:02:30 (HH:MM:SS) will pass just below the Moon. It will then pass through the top of the constellation Sagittarius and then be 29 degrees above the southeastern horizon at 8:03:34. It will pass above Saturn, low in the east southeast, at 8:05:30 and will move into the Earth’s shadow and fade from view low in the east at 8:06:45.
Thursday night there will be a late, high pass of the ISS across the northwestern sky, and the space station will move into the Earth’s shadow and vanish from view when high in the sky.
On Thursday look for the ISS rising from the west southwestern horizon after 8:50 P.M. By 8:52 the ISS will be 30 degrees high and moving toward Corona Borealis. It will pass through Corona Borealis just before 8:53, then traveling between Hercules and Boötes. At magnitude -3.4 when high in the sky, the ISS will be easy to spot.
The ISS will then pass through Draco and above Ursa Minor, passing well above Polaris, the North Star, just after 8:54. As it approaches the familiar “W” of stars marking Cassiopeia, the Queen, it will move into the Earth’s shadow and fade from view.