Unfortunately we have had some challenging weather conditions recently so it hasn’t been beneficial for observing the night sky. However, as usual, the Blue Moon at the end of August made the headlines in the media.
The following chart represents the night sky at 11.00pm BST on the 8th of September and at 10.00pm BST on the 23rd September. To use the chart, face your southern horizon at the appropriate time and you will see the stars in the chart.
There is more on the chart than we really need but it helps to show where everything is with respect to each other. The constellation Andromeda is included but we will discuss that in more detail next month. This month the constellation of interest is Pegasus- The Winged Horse. The bottom edge of Cassiopeia and the Summer Triangle (outlined in red) are included just so that we can find our way about. So facing your southern horizon and looking up towards your zenith you will see the bright star Deneb, the tail of Cygnus the Swan, and further right the even brighter star Vega which enables us to pick out the Summer Triangle with Altair closer to the horizon. It is always good to see the Summer Triangle but now look eastwards and towards your zenith and you will find Cassiopeia. You should now be able to pick out the asterism, the Great Square of Pegasus, lying below Cassiopeia and to the east of the Summer Triangle. It stands out not because its stars are particularly bright but because it covers a pretty empty area of the sky. The constellation Pegasus doesn’t really bear any resemblance to a winged horse but the Great Square is easily recognised. The brightest star in the square, Alpheratz, at magnitude 2.1 is actually in the constellation Andromeda. The stars, Markab and Scheat, are similar in brightness with magnitudes of 2.5 and 2.7 respectively, but the former is a blue-white star while Scheat is a red giant variable. The final star is marginally dimmer at magnitude 2.8.
Something to look out for
There will be a close approach of the Moon and Jupiter on Monday 4th September, visible after 10.00pm just after Jupiter rises in the east. There is the Perseid meteor shower best seen around Saturday 9th September but the hourly rate of sightings is likely to be quite low. If you are an early bird, Venus will be at its brightest and highest altitude in the east on the early morning of Monday 18th September. Time moves on and there is the autumn equinox for the northern hemisphere on Saturday 23rd September.The Sun will rise due east and sink due west so perhaps you will be able to fix directions with a suitable landmark. More importantly for astronomers there will be more hours of darkness than daylight thereafter. Finally there will be a close approach of the Moon and Saturn on the 27th September. Of course the Moon will be obvious but the position of Saturn is shown in the chart and although visible throughout the evening it reaches its highest position in the sky about 11.00pm BST.