The September night sky highlights include Comet C/2023 A3 (Tsuchinshan-ATLAS) in the morning sky. A dawn appearance by Mercury. A partial eclipse of the Moon and Saturn at its very brightest. This month as the nights become longer and we move towards unsettled weather. The autumn constellations are starting to show. Ursa Major, or the Plough, can be found low in the North. The ‘W’ of Cassiopeia is not far from the overhead point. Also on view this month we have the watery constellations. Aquarius the water carrier, Cetus the sea monster, Capricorns the sea goat, Pices the fishes, Piscis Austrinus the southern fish and Delphinus the Dolphin.
The summer triangle of Altair, Deneb and Vega remains high up. The southern sky is dominated by the Square of Pegasus. The bright star Capella in the constellation of Auriga the Charioteer is becoming more noticeable in the east. It will be overhead in winter evenings.
Although the four stars that form the Square of Pegasus are not the brightest, once found they will be easily recognised again. It is always an interesting project to count how many stars you can see within the square; you might be surprised by the result.
If you use the two right hand stars of the square and draw a line to the south you will reach a bright star very low in the sky. This star is Fomalhaut, in the constellation of Piscis Austrinus.
The Planets:-
MERCURY
During the first two weeks of September the inner most planet puts on its best morning show of the year, low in the eastern sky before dawn breaks.
Mercury will be at its greatest elongation on the 5th of this month. Shinning at magnitude –0.2 it rises above the horizon about 4.40am. Mercury grows brighter; passing the star Regulus on the morning of the 9th September. But by the middle of the month it has sunk so low that it will be lost in the twilight glow.
VENUS
Very low in the western sky after sunset, the evening star is hugging the horizon all month. Binoculars will help you spot it in the glowing twilight sky. Venus is in all it’s brilliant glory at magnitude –3.9, and falls below the horizon about 8pm. The thin crescent Moon will be close to Venus on the 5th of the month.
MARS
The red planet moves from the constellation of Taurus and into neighbouring Gemini as the month progresses. Gliding below the pretty star cluster M35 on the nights of the 8th and 9th of September. Shinning at magnitude +0.6 Mars rises above the horizon around 11.30pm.
JUPITER
The gas giant Jupiter, rises about 10.30pm, at magnitude –2.4. Located in the constellation of Taurus. The almost half Moon will be close by on the 23rd of this month.
SATURN
The ring world lies in the constellation of Aquarius and is above the horizon all night long. At a magnitude of +0.6, it is shinning at it’s brightest this year. A low power telescope will reveal its Famous rings currently appearing almost edge on, along with its biggest moon, Titan. On the night of the 8th of this month Saturn is opposite to the Sun and at it’s nearest to the Earth at 1295 kilometres.
URANUS
Found in the constellation of Taurus. It rises above the horizon about 9pm. At magnitude +5.7 it is just visible to the naked eye, but is much better seen with optical aid.
NEPTUNE
Neptune is located in the constellation of Pisces. The most distant planet is at opposition to the Sun and it’s closest to Earth on 20th September, and is above the horizon all night long. But even at opposition, Neptune only reaches magnitude +7.7, so you well need binoculars or a low power telescope to see it.
PLUTO
This distant planet can be observed in a ten-inch or larger telescope. It can be found in the constellation of Capricornus, at magnitude +14.5. It will be setting just after 1.15am.
CERES
The largest object in the asteroid belt can be located in the constellation of Sagittarius. At magnitude +8.7 it should be visible through binoculars or a low power telescope. Setting around 10.40pm.
Special Events: –
5th September – Before dawn, Mercury is at its greatest
separation from the Sun
5th September – The thin crescent Moon is close to the brilliant evening star Venus.
8th September – Saturn is opposite to the Sun, and nearest to the Earth at 1295 million kilometres.
8th and 9th September – Mars passes below the M35 Shoe buckle star cluster.
18th September – The first of three supermoons this year, suffers a partial eclipse visible from Europe, Africa and America. But only eight percent of the Moon is obscured by the Earths shadow at maximum eclipse at 3.44am. The eclipse lasts from 3.12am to 1.15am.
20th September – Neptune is opposite to the Sun, and nearest to the Earth at 4322 million Kilometres
22nd September – The nights become longer as we pass through the autumn equinox.
23rd September – The almost half Moon is just above and close brilliant Jupiter.
28th September – Comet C/2023 A3 (Tsuchinshan-ATLAS) will be visible to the naked eye in the pre dawn sky shining as brightly as magnitude. +0.6, but rising just before the Sun. Our best views of A3 will come when it moves up into the evening sky around 12th October.
The phases of the Moon for September are:-
New Moon 3rd September
First quarter 11th September
Full Moon 18th September
Last quarter 24th September