Skywatch Line for Monday and Tuesday, September 15 and 16, 2025, written by Alan French

This is Dudley Observatory’s Skywatch Line for Monday and Tuesday, September 15 and 16, 2025, written by Alan French.

The Sun rises at 6:35 A.M. on Wednesday and sets at 7:05 P.M. On Thursday it rises at 6:36 A.M. and sets at 7:03 P.M.

The Moon is moving toward new and rises after midnight, so the evening skies are dark. Moonrise on Tuesday is at 12:30 A.M. and on Wednesday it rises at 1:47 A.M. If you are up around 5:30 A.M. Monday a waning crescent Moon, 39% sunlit, will be high in the east southeast among the stars of Auriga, the Charioteer. At 5:30 A.M. Tuesday the Moon, 28 ½% sunlit, will be 48 degrees above the eastern horizon and will be in Gemini, with Castor 6 degrees away and Pollux almost 5 degrees from the Moon. Bright Jupiter will be 4 ½ degrees to the lower right of the Moon.

If you look high in the south at 8:45 Thursday morning, you will find a pale crescent Moon in the blue sky. The Moon will be new next Sunday.

Venus continues in the morning sky before sunrise, now just over 13 degrees high at 5:30 A.M. and 24 degrees above the horizon by 6:30 A.M. It shines at magnitude -3.9 and, just less than 12 light minutes from Earth, appears as a small, 11.6 arcsecond disk, 88% illuminated in a telescope. Because of its low altitude and extreme brightness, it can be hard to get a good view of the planet with a telescope. Its highly reflective clouds are also featureless in visible light.

The ISS is most impressive and brightest when it travels high across our skies but its lower passes can also be fun to watch. There are nice passes low across the northern skies on both nights. The pass Wednesday is later and under darker skies, otherwise they are very similar.

On Wednesday look for the ISS coming low across the northwestern sky at 8:59 P.M. Just after 9:00 P.M. it will begin passing along the bottom of the Big Dipper’s bowl, its path will then take it well below Polaris, the North Star, and soon after 9:02 it will move into the Earth’s shadow and fade from view. At its brightest it will reach magnitude -1.5.

Thursday’s pass will first be visible around 8:10 P.M. low in the west-northwest and will be slightly lower than the pass Wednesday. Soon after 8:11 it will be passing below the Big Dipper’s bowl and by 8:12 the space station will be past the Bowl. It will pass well below Polaris just before 8:13. By 8:14 it will be approaching the stars of Perseus low in the northeast. Just after passing through the stars of Perseus the ISS will move into the Earth’s shadow and fade from view. At its brightest it will be at magnitude -1.6.