September 2021 Astronomy

September 2021 Astronomy

You will be noticing a couple of bright star-like objects in the southeast—in the constellation Capricornus.

You can consider going out on your celestial walkabout earlier in the evening. Our ancestors went to bed at sunset and rose with the sun in the morning, but we have other distractions that keep us up at night, to our physical and mental detriment. Astronomers are doomed to stay up a bit too late. But I think looking at the night sky must be better for me than cruising the internet or texting trivia. You will be noticing a couple of bright star-like objects in the southeast—in the constellation Capricornus. These are the planet Saturn on the right and Jupiter on the left. Saturn is best known for its vivid rings of dust and icy particles, but you will need an optical aid to see them. Typical binoculars may show a tiny and slightly elongated disc. A small telescope makes the rings obvious. Jupiter is about half the distance and inherently larger, so binoculars clearly show a disc. Holding or supporting the binos will also let you see its four brightest moons, the Galilean moons. You can watch and sketch their positions as they change from night to night.


Sep 6 New moon; Aquila (Altair) on meridian at 10 p.m.
Sep 13 First-quarter moon
Sep 14 Mercury max elongation (26.8 degrees – eve)
Sep 16 Sun enters Virgo
Sep 18 Cygnus (Deneb) on meridian at 10 p.m.
Sep 20 Full moon
Sep 21 Capricornus, Saturn and Jupiter near meridian at 10 p.m.
Sep 22 Autumnal Equinox at 03:21
Sep 28 Last-quarter moon


Dates for the Phases of the Moon

Entries are in eastern time and only require time zone correction. Do not use the correction from the Ottawa Time Corrections table.
Saskatchewan and parts of British Columbia and Ontario do not use daylight time. In these regions, subtract 1 hour from these times
from March 14 to November 7.

Planetary Configuration

When at opposition, planets will appear on the opposite side of the sky from the sun—very roughly on the meridian at midnight.
A conjunction is when the planet has the same “longitude” as the sun. A superior conjunction is when the planet is on the other side of the sun, and an inferior conjunction is when it is between Earth and the sun. Only Mercury and Venus can be at inferior conjunction. Maximum elongation is when Mercury and Venus appear farthest from the sun in our sky. This occurs either in our morning eastern sky (morn) or our western evening sky (eve).
Do not apply the Ottawa Time Corrections to the times in this table.

Prominent Constellations By Seasons

Prominent Constellations for Summer 2021

Brightest Stars

Star NameScientific NameDistance (Light-Years)Midnight Transit
FomalhautAlpha PsA25Sep 19

Ottawa Correction Table

Ottawa Correction Table
Robert Dick
Robert Dick

One of Canada’s foremost writers and educators on astronomical topics, the Almanac has benefited from Robert’s expertise since its inception. Robert is passionate about reducing light pollution and promoting science literacy. He has been an astronomy instructor for our astronauts and he ensures that our section on sunrise and sunset, stargazing, and celestial events is so detailed and extensive it is almost like its own almanac.

By The Same Author:

Posted on Wednesday, September 1st, 2021
Filed under Environment | Nature

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