Skywatch Line for Monday and Tuesday, March 17 and 18, 2025, written by Alan French
This is Dudley Observatory’s Skywatch Line for Monday and Tuesday, March 17 and 18, 2025, written by Alan French.
The Sun rises at 7:03 A.M. on Monday and sets at 7:04 P.M. With just over 12 hours 1 minute of daylight, Monday, St. Patrick’s Day, is the first day this year with more than 12 hours of daylight. On Tuesday the Sun rises at 7:01 A.M. and sets at 7:06 P.M.
The Moon was full early last Friday morning and we enjoyed a total lunar eclipse. Although early forecasts were pessimistic, the skies in this area cleared for the eclipse and a reddish, fully eclipsed Moon was visible for 1 hour 6 minutes. This observer, and others, found the coloration most obvious by eye, and subdued in binoculars. The Moon is now moving toward last quarter and rises late in the evening.
On Monday night the 87% sunlit, waning gibbous Moon rises in the east southeast at 10:46 P.M. It will be due south and 27 degrees high at 3:44 A.M. Tuesday and will not set until 8:34 A.M. If you are up around 6 A.M. Tuesday look for an 85% illuminated Moon low in the southwest.
Tuesday night the Moon rises at 11:51 A.M. in the southeast. It will appear just less than 80% sunlit, will be south at 4:30 A.M. Friday, will be low in the south southwest at 6 A.M. Friday morning, and set at 9:01 A.M. The Moon will reach last quarter on Saturday.
Venus and Mercury are no longer easy to spot, Mercury will be especially difficult. Thirty minutes after sunset, Venus is only 4 degrees above the horizon, 9 degrees north of due west. You will need a good view low in that direction to spot it. However, our neighboring planet is still at magnitude -4.2, which should make it easy with the right location and clear skies. It is a slender, 2% sunlit crescent, almost 59 arcseconds in diameter. The crescent can be seen in steadily held binoculars and any telescope, but the view may be hampered by the thick atmosphere we look through low in the sky.
Mercury is higher in the sky, just under 6 degrees high 30 minutes after sunset, but has faded to magnitude +2.3, making it difficult or impossible to spot against the evening twilight. It lies 6 degrees to the north and slightly higher than Venus. Mercury appears only 9.8 arcseconds across and is also a crescent, just under 10% illuminated. Venus sets just after 8 P.M. and Mercury sets just before 8:10.
With the Moon rising late the early evening hours will feature dark skies, especially away from city lights.
High toward the south at 9 P.M., 72 degrees above the horizon and shining at magnitude +0.1, you will find reddish Mars. The Red Planet is in the constellation Gemini, the Twins. The two bright stars to the upper left of Mars, Pollux, closest, and Castor, are the constellation’s brightest, with Pollux the brightest of the pair.
The constellation is easy to picture. The outlines of Castor and Pollux are created by a line of stars going down to the lower right from each star. It is easy to imagine The Twins, side-by-side in the night sky. Mars lies closest to the figure of Pollux.
Near Castor’s feet, on the side opposite his brother, is a nice globular cluster, a huge ball of stars, visible by eye under dark skies as a fuzzy spot. It is better seen in binoculars and a lovely sight in a small telescope at low powers. The cluster spans 30 arcminutes and contains more than 100 stars from 6th to 13th magnitude.