Skywatch Line for Monday and Tuesday, September 8 and 9, 2025, written by Alan French

This is Dudley Observatory’s Skywatch Line for Monday and Tuesday, September 8 and 9, 2025, written by Alan French.

The Sun rises at 6:28 A.M. on Wednesday and sets at 7:17 P.M. On Thursday it rises at 6:29 A.M. and sets at 7:15 P.M.

The Moon was full on Sunday and is now moving toward last quarter. The Moon rises at 7:44 P.M. on Monday. It will rise in the east and the waning gibbous Moon will be 98% in sunlight, appearing almost full. By 9 P.M. the Moon will be 13 degrees above the horizon and the skies dark enough to spot Saturn to the south (right) of the Moon. Saturn will be just under 6 degrees from the Moon.

Saturn will be due south at 1:48 A.M. on Tuesday and 44 ½ degrees above the horizon, well placed for observations with a telescope. The Moon will then be almost 8 degrees from Saturn.

Saturn is moving eastward among the stars and rising earlier each night, so it will eventually be well placed for evening observing. In one month, Saturn will be due south and highest at 11:33 P.M. By November 8 the planet will transit at 8:29 P.M.

Tuesday night’s Moon rises at 8:06 P.M. a little west of due east and will be 93% illuminated. It will be south at 2:55 A.M. Friday and set at 9:59 A.M. It will reach last quarter next Sunday.

They only other naked-eye planet in the evening sky is Mars, and it is low in the west southwest as twilight falls and sets at 8:32 P.M. Mars is now 343.4 million km from Earth, shines at magnitude +1.6, and appears as a tiny 4.1 arcsecond disk through a telescope. At its closest and best, Mars is 56 million km from Earth, appears 25 arcseconds across, and shines at magnitude -2,9. At Mars’ next opposition on February 19, 2027, it will be 101 million km from Earth, appear 13.8 arcseconds across, and shine at magnitude -1.2.

Venus and Jupiter are in the morning sky. At 5:30 A.M. Venus will be 16 degrees above the horizon toward the east and Jupiter will be 41 degrees above the western horizon and near Castor and Pollux. Venus is now a small, 11.9 arcsecond disk and 86% illuminated as it continues to move toward the opposite side of the Sun from Earth.