September Skies

- By James Edgar

September 1, 2025

So, on September 7, at 11:08 p.m. UT (5:08 p.m. CST), the Moon is at the ascending node. Ascending meaning moving from south to north, descending goes the other way. A node-crossing event brings about an eclipse season–twice a year, sometimes three times a year. Thus, on September 7, the Sun, Earth, and the full Moon line up such that Earth’s shadow darkens the Moon–a lunar eclipse. The event lasts a couple of hours and can been seen from most of the Eastern Hemisphere; unfortunately not visible in the Western Hemisphere. Fourteen days later, a solar eclipse occurs during new Moon, only visible from the extreme South Pacific and Antarctica. In the meantime, we have some planetary and stellar close calls to observe. On the 8th, Saturn and Neptune are within 4 and 3 degrees of the Moon, respectively. The Pleiades are 1 degree away on the 12th. By the 16th, Jupiter is 5 degrees south of the waning crescent Moon, and the following day it’s 2 degrees north of the Beehive Cluster (M44). The morning of the 19th sees a trio of the Moon, Regulus, and Venus. The 23rd sees Spica in Virgo only 1.1 degrees from a barely visible thin crescent Moon. Mars is 4 degrees north on the 24th and Antares (the opposite of Mars/Ares) is 0.6 degrees north on the 27th.

Mercury is behind the Sun, or too close to observe, all month.

Venus remains a Morning Star in the eastern dawn. Watch for a trio of Venus, Regulus, and the crescent Moon on the 19th.

Mars is tiny but visible in the western evening twilight. It passes 2 degrees north of Spica on the 12th.

Jupiter is prominent in the evening sky and through the night. The waning crescent Moon passes 5 degrees to the north on the 16th. Toward the end of the month, a series of double shadow transits of two Galilean moons occur at 3.5-day intervals.

Saturn is at opposition in Pisces on the 21st, so the closest to us and furthest from the Sun, making for prime observing and astrophotography. The Ringed Planet will be in retrograde motion for most of the month. Watch for the Moon nearby on the 8th.

Uranus begins retrograde motion on the 6th among the stars of Taurus, just to the south of the Pleiades. Its apparent westward motion continues for nearly six months.

Neptune is in southern Pisces all month, along with Saturn, and reaching opposition on the 23rd. At its extreme distance from the Sun, the reflected light takes 4 hours to reach us.

The zodiacal light is visible before eastern morning twilight for the last two weeks of the month.

The autumnal equinox occurs in the afternoon of September 22.