This month the nights become longer and we move towards unsettled weather. It is not often that the distant worlds are the one’s to look at, but this September Neptune is not only at its closest, but performs a rare pas-de-deux with a leading star in Aquarius. 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, 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.
Jupiter is brilliant in the evening sky, blazing at magnitude –2.1 low in the south west in Ophiuchus. The Giant planet sets about 10.30pm.
Saturn is located in Sagittarius, in the southern sky. With a magnitude of +0.4 it sets around 0.30am.
This month it is the outermost planets time to shine. Neptune is at opposition to the sun and closest to the Earth on the 10th of the month. A mere 4,328 million Km away from us. The gas giant will be visible throughout the whole night. With a constant dim magnitude of +7.8.
You can see it in binoculars or a low power telescope. The problem always knowing exactly where to point your instrument as Neptune does tend to become lost among all the other faint stars. This month though, it’s a bit easier. Neptune is very close to a star that is relativly bright; Phi Aquarii (Magnitude +4.2). Between 3rd and 9th September, the star cloest to Phi Aquarii and 25 times fainter is Neptune. On the 6th Neptune is only half an arcminute to the right of Phi Aquarii. You will be hard pushed to separate the two in binoculars, and a telescope will reveal a stunning red and green ‘double star’.
Uranus rises at 8.30pm, at magnitude +5.7 in Aries.
Mercury, Venus and Mars are too close to the sun for observation.
During the night of 19th to 20th, the waning Moon lies below the Pleiades, and during the night moves towards the Hyades and Aldebaran.
23rd September is the Autumn Equinox, and the nights slowly become longer for the next three months.
The phases of the Moon for September are:-
First Quarter 6th
Full Moon 14th
Last Quarter 22nd
New Moon 28th