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Home / Explore / Astronomy Info & Events: September

Astronomy Info & Events: September

The Visible Planets

Mercury is not visible in the early days of the month as it is at inferior conjunction on September 6. After inferior conjunction, Mercury emerges out of the sun’s early morning glow by September 13, becoming visible low along the eastern horizon. From September 13 to the end of the month, Mercury puts on a great showing from our location in the predawn eastern sky. This is the best viewing opportunity all year for us for this elusive planet. Mercury will be at its point of greatest western elongation (18°) from the Sun on September 22. Look for Mercury just below the waning crescent Moon before sunrise on September 13.

Venus shines brilliantly as the so-called “morning star” in the eastern sky before sunrise all month long. The waning crescent Moon will appear above bright Venus above the eastern horizon before sunrise on September 11. On September 19 Venus will be at its greatest illuminated extent, shining with a magnitude of -4.8, which is the brightest it ever appears.

Mars is not visible from our latitude this month. From our location, Mars has disappeared into the light of the setting Sun at the end of last month. On September 16, there will be an occultation of Mars by the very slim waxing crescent Moon from 12:07 p.m. to 1:25 pm that can be viewed with some difficulty through a telescope. The best moments to view this event would be immediately before the occultation and then again immediately after Mars reappears from behind the Moon.

Jupiter rises along the east-northeast horizon at around 10:00 p.m. at the start of the month and by 8:00 p.m. at the end of the month. It is located within the constellation of Aries, the ram, where it stays all year long. Through the night, you can watch Jupiter slowly progress westward in the southern sky until it is found high, about 51°, in the southern sky late in the evening. Jupiter will be near the waning gibbous Moon through the overnight hours of September 3 and 4.

Saturn is seen rising along the southeastern horizon at sunset, traversing the southern sky through the night, and then setting along the southwestern horizon by the time of sunrise. Having just passed its date of opposition back on August 27, Saturn still provides for nice telescopic views during the month of September. Saturn is seen as the brightest object amongst the stars of Aquarius, the water bearer. On the night of September 26, look for Saturn just above the waxing gibbous Moon.

Moon Phases

September 6 Last Quarter Moon

September 14 New Moon

September 22 First Quarter Moon

September 29 Full Moon (The Harvest Moon or Corn Moon)

Special Events

International Space Station (ISS) Observable Passes

During the month of September there will be several favourable passes of the ISS. From September 1 to September 9, observable passes of the ISS will be found in our predawn morning sky. From September 14 to October 4, the ISS passes appear at more favourable early evening passes between 7:00 p.m. and 11:00 p.m. Check the website http://www.heavens-above.com for exact viewing times for your location.

September 3 Venus is stationary

September 6 Mercury is at inferior conjunction (in between the Earth and Sun)

September 11 Royal Astronomical Society of Canada (RASC) Edmonton Centre meeting

Live in the Zeidler Dome at TELUS World of Science - Edmonton and presented virtually through Zoom.

7:30 p.m. – 9:30 pm

Free for anyone to attend.

See http://www.edmontonrasc.com for more details.

September 12 to 17 Northern Prairie Star Party 2023

Black Nugget Lake, AB

See https://edmontonrasc.com/northern-prairie-star-party/ for details.

September 16 Occultation of the planet Mars by the slim waxing crescent Moon

September 19 Neptune at opposition

Venus at its greatest illuminated extent (magnitude -4.8) Very bright!

100th Anniversary of the first optical mechanical star projector, the Zeiss “Mark 1” projector! Celebrations for the 100th anniversary of the planetarium begins! See https://planetarium100.org/ for more on this historic anniversary.

September 22 Mercury is at its greatest elongation west (18°)

Lunar straight wall visible tonight!

September 23 Fall equinox occurs at exactly 0:50 a.m. MDT

September 24 NASA's Osiris-Rex asteroid Bennu sample returns to Earth.