What’s Up in the Night Sky? September 2021

Fred Barrett | Sep 01, 2021

Every September in the northern hemisphere, we have the autumnal equinox. This year it occurs on September 22nd. It marks the start of fall. A second equinox occurs each year in March. It is called the vernal equinox and signals the start of spring. After the autumnal equinox, the days get shorter and the nights get longer as we’re dragged kicking and screaming towards winter. The vernal equinox is the opposite. We happily go along with longer days and shorter nights and summertime. In the southern hemisphere, the seasons are opposite to ours in the north.

At the moment of the equinox, the Sun is directly above the equator. Remember that the Earth doesn’t spin around an axis directly straight up and down. It has a tilt of 23.4 degrees. This means that as the Earth orbits the Sun, the tilt of the northern hemisphere inclines more towards the Sun in summer and away from the Sun in winter. An equinox marks the point when the change of tilting away or towards the Sun begins; in other words.

The moment when the maximum tilt of the Earth is farthest away or towards the Sun is called a solstice. These occurs halfway between the equinoxes. The word for “equinox” is a mix of 2 Latin words: ‘aequus’, for equal and ‘nox, for night.

I promised a new contest for September and here it is. The winning prize is the same as last time: the beautiful and informative book “The Elements” by Theodore Gray. The colourful photographs and easily understood text in this book is a very useful reference for young students and adults and a perfect guide for understanding the universe. Ok, here’s the question:

“What do astronomers call the position of the Moon’s orbit on September 26th?” To help me choose the winner from the entrants that have answered correctly, describe for me some interesting things about the Moon’s orbit around the Earth. Impress me. Send answers to my email address or to the editor.

During September, before midnight, 6 planets can be found with your binoculars and telescopes. Neptune is in the south and Uranus is in the east at mid evening. Neptune is in opposition on the 14th and, at a magnitude of 7.7, can be seen in binoculars. You’ll have to do a little research to find its position in the sky. On September 19th it’s 6 degrees north of the Full Moon. Venus is bright in the west just after sunset but close to the horizon. Note a special event: the Moon passes just above and to the north side of the Moon on the 9th. Jupiter and Saturn are spectacular in the southeast in the evening. By midnight they are more to the south and high at 35 degrees. Get your binoculars out and enjoy the moons of both planets. Use your cell phone to catch pictures. Experiment with the zoom function or try to get a picture through your binoculars. Please email me what you get and your experiences getting the pictures. I just recently started using my cell for quick astronomy images. It’s a lot of fun and the results can be surprising in a good way!

Monthly Highlights

Sept. 5: Venus passes just north of Spica low on the western horizon soon after sunset. An almost new Moon is close by and to the right. Mercury, although dim, is a bit below Spica and the Moon.

Sept. 6: New Moon.

Sept. 8: The Moon passes 7 degrees north of Mercury about 10pm.

Sept. 11: The Moon is at perigee – 366,322 Kms.

Sept.13: First Quarter Moon

Sept. 14: Neptune is in opposition.

Sept. 16: The Moon can be found 4 degrees south of Saturn at 11pm.

Sept. 18: The Moon is 4 degrees south of Jupiter at 3am.

Sept. 20: The Moon is 4 degrees south of Neptune at 5am. It’s also a Full Moon. This Full Moon is called the Cenqolew (Dog Salmon) Full Moon by western first nations. It’s also known as the Full Corn Moon or the Full Harvest Moon. For me, it marks the beginning of the best season for observing. The nights are clear and have the cool organic smell of fresh fallen leaves and all the bugs are hibernating.

Sept. 22: Autumnal Equinox.

Sept. 26: The Moon is at Apogee – 402,291 Kms.

Sept. 28: Last Quarter Moon.

Stay safe and keep looking up!

Useful books, star charts and related items for beginners and through to advanced amateurs can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. A subscription to our very own excellent Canadian astronomy magazine “SkyNews” can be arranged at the RASC website as well.

Let me know how your observing has gone this month, especially anything unusual. I enjoy the feedback. If you have any questions or suggestions you can contact me through this paper or email me at This email address is being protected from spambots. You need JavaScript enabled to view it. . Clear Skies! Fred