What's Up in the Night Sky

September 2025 - Vol. 29, No. 9

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

The Summer Triangle asterism, Vega (Lyra), Deneb (Cygnus) and Altair (Aquila), is still quite prominent overhead as darkness falls. Arcturus (Bootes) is now dipping to the NW horizon. From a dark site, the myriad stars of the Milky Way (the visible "arm" of our galaxy), "flow" eastwards through the "W" asterism of Cassiopeia and to bright Capella (Auriga) glowing in the NE. "The Great Square of Pegasus" asterism burns high in the SE while lonely Fomalhaut (Piscis Austrinus) shines far below, very close to the horizon. "The Big Dipper" asterism (Ursa Major) is nearly horizontal and now sits low on the N horizon. In the E, Aldebaran (Taurus) shines, a sure sign of Autumn.

MERCURY, at superior conjunction is not visible this month. VENUS, in the morning sky, joins Regulus and the Moon on the 19th for a nice conjunction. MARS, visible in the evening sky, shines at +1.6 magnitude in Virgo with a 4" disc. JUPITER rises in the morning sky, shining at -2.1 magnitude by month's end. SATURN reaches opposition on September 21, in the constellation of Pisces. URANUS rises before midnight with the constellation Taurus. NEPTUNE rises in the evening sky, reaching opposition on September 23. (You'll need a telescope to observe Neptune.)

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Venus 1.5 deg. S. of the M-44 open star cluster also called the Beehive cluster.
04	Pluto, 0.06 deg. S. of Moon, occultation from Madagascar, most of Australia parts of SE Asia, Melanesia, most of Micronesia.
06	Uranus stationary.
07	A total lunar eclipse will occur, beginning at 15:28 UT. This eclipse favors the Eastern hemisphere: Europe (partial), Africa, Middle East, India, Asia, Australia, and New Zealand. September's full moon is often called the "Harvest Moon" because it is the time of year that farmers in North America harvest many crops. Mercury at greatest heliocentric lat. N.
08	Saturn 4 deg. S. of Moon. Neptune 3 deg. S. of Moon.
10	Moon at perigee.
12	Moon 1.0 deg. N. of the Pleiades star cluster (M-45). Mars 2 deg. N. of Spica.
13	Mercury at superior conjunction.
16	Jupiter 5 deg. S. of Moon.
17	Moon 2 deg. N. of the Beehive cluster (M-44).
19	The Zodiacal Light or "false dawn" is visible in the E about 2 hours before sunrise. This pyramidal glow is caused by meteoroids, dust particles spawned by passing comets, etc., that have settled into the ecliptic plane (path followed by the Sun, Moon and planets), reflecting the Sun’s light before it rises here. This phenomenon will be visible for the next two weeks. Venus meets up with Regulus in the constellation of Leo and the Moon for a nice conjunction. Venus will be 0.5 deg. N. of Regulus. Venus 0.8 deg. S. of the Moon, occultation from NW Canada, Greenland, Iceland, Europe, W. Russia, parts of the Middle East, NE Africa. Alpha Leonis, Regulus, 1.3 deg. S. of Moon, occultation from Urals region of Russia.
21	Saturn at opposition. partial solar eclipse visible from South America and Antarctica. The moon will cover 85% of the Sun's disk at greatest eclipse.
22	Equinox, the Sun rises due East and sets due West. Autumn begins in the northern hemisphere.
23	Alpha Virginis, Spica, 1.1 deg. N. of Moon, occultation from S. New Zealand, Tasmania, parts of Antarctica. Neptune at opposition.
24	Mars 4 deg. N. of Moon.
26	Moon at apogee.
27	Alpha Scorpii, Antares, 0.6 deg. N. of Moon, occultation from Easter Is., S. part of South America, most of Antarctica, Kerguelen Is., Marion Is.

Lunar Almanac for September 2025

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 21	Deep Space Objects
	1st. Qtr 29	Planets & Moon
	Full 07	Moon
	Last Qtr 14	Deep Space & Planets

Topic of the month: Cygnus, the Swan

During the month of August, the constellation of Cygnus, the swan, dominates the night sky and the summer Milky Way. High overhead after darkness chases away the long summer twilight, the swan flies. The brightest star of the constellation is Deneb, a blue giant that is among the 20 brightest stars in the night sky. A blue giant star, Deneb is designated Alpha Cygni and forms a large triangle known as the Summer Triangle with the bright stars Vega and Altair.

The constellation is thought to resemble a bird. Because it is so far north, it spends a lot of time in the northern sky, visible all year round from northern locations. (Although it may not be visible all night.) If you have trouble seeing a bird, you may resonate with Cygnus's other identify, the constellation is often called the Northern Cross. If you watch the cross all night in August from the northern hemisphere, you will notice that it twists in the sky, so that by the time it sets, it appears to hang upright over the western horizon. It is rather fascinating that the cross will be in this position in the inky evening sky on December 25.

Another beautiful star in the constellation is Beta Cygni, known as Albireo. Albireo is a beautiful double star. In a small telescope the stars appear bright yellow and blue. The pair may also be split with binoculars. The central star of the Northern Cross is the second-magnitude star, Sadr, interesting to view in a small telescope. The star fields of the Milky Way between Albireo and Sadr are magnificent. Notable galactic clusters in Cygnus include M29, M39, NGC 6819 and NGC 6866.

The Milky Way in the constellation of Cygnus offers much in the way of bright and dark nebulae, for it is here that the "Great Rift" of the Milky Way begins. This rift is the same dark lane that we can observe in distant spiral galaxies, for the dark material of the rift absorbs light from the stars. It is composed of gas that someday may form new stars in our galaxy. For deep sky observers, Cygnus offers one of the finest supernova remnants known as the Veil Nebula. The star that formed this magnificent nebula exploded over 5,000 years ago, its spreading debris field now covers over 3 degrees of the sky for Earth based observers. This expanding wreath of gas has two separate designations, NGC 6960 and NGC 6992. The western portion of the veil (NGC 6960) is located near the star 52 Cygni while the eastern portion displays fabulous filamentary structure. For bright nebulae, Cygnus offers NGC 7000, the North American Nebula approximately 3 degrees E of Deneb. So called for it's resemblance to the continent, this bright field may be noted with the naked eye at a dark site. It is often seen in binoculars and a small telescope will yield its brightest jewels.

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. The above image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Editing was done for educational purposes only. Stellarium offers much more to amateur astronomers and is being used in planetariums and to guide telescopes in the field. Simple charts like the one above can be used on the internet for non-profit, illustration purposes. Proper credit is due of course! Thank you to the makers of this fine program from Astra's Star Gate.