Skywatch Line for Wednesday and Thursday, November 19 and 20, 2025, written by Alan French
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, November 19 and 20, 2025, written by Alan French.
The Sun rises at 6:53 A.M. on Wednesday and sets at 4:29 P.M. On Thursday it rises at 6:54 A.M. and sets at 4:28 P.M. This Thursday has lost just over 14 ½ minutes of daylight compared to last Thursday.
The Moon will be new at 1:47 A.M. EST on Thursday morning, so the Moon is close to the Sun. On Wednesday it rises at 6:27 A.M., just 23 minutes before sunrise, in the east northeast, and will be essentially lost in morning twilight. On Thursday the young Moon rises after sunrise and sets before sunset.
Thursday’s new Moon is the start of lunation 1276. The numbering of lunations started with lunation 1, the new Moon on January 16, 1923. A mathematics professor at Yale University, Ernest William Brown, is responsible for the numbering of lunations.
Brown was born in England in late 1866. He studied mathematics at Christ’s College, receiving his degree in 1887. He received a Doctor of Science (Sci. Dr.) from Cambridge in 1897, a mark of deep mastery of celestial mechanics and original research. He was especially interested in the motion of the Moon. He worked on extending the lunar work of American astronomer George William Hill and revised it to use more modern mathematical tools. He joined Yale University in 1907 as professor of mathematics and stayed until his retirement in 1932.
The Hill-Brown Lunar Theory was adopted as the basis of lunar ephemerides in nautical almanacs in 1923, and the first new Moon of 1923 became lunation 1. The theory was used for accurate lunar tables and lunar and solar eclipse predictions until its retirement in 1984. It was replaced by the JPL Development Ephemerides.
Saturn is now due south and highest at 7:45 P.M. Wednesday and 7:41 on Thursday. The rings are less than a week away from their thinnest appearance and are tipped about ½ degree, with their southern face slightly toward us. Through a telescope the typical unsteady skies of winter may make the slender rings hard or impossible to spot.
The brightest moon of Saturn, Titan, can usually be seen in almost any telescope. The second brightest, Rhea, might require a telescope of 70 or 80mm aperture. Tethys and Rhea often require 5 or 6-inches of aperture. With the rings near edge on and dimmer than usual, they might be possible in smaller telescopes.
On Wednesday night around 7:45 P.M. all these moons will be to the east of Saturn. The brightest, Titan, will be well to the east, over 8 times Saturn’s diameter away. Rhea will be about 2 ½ Saturn’s diameters to the east. Dione will be very close to Rhea, and Tethys will be about halfway between Rhea and Saturn.
On Thursday around 7:45 Titan will still be to the east of Saturn, but a little closer to the planet. Rhea will be less than three planet diameters to the planet’s west, with fainter Dione nearby. Tethys will be closer to the planet than Rhea.
How many of the moons can you spot? Do you see the rings?