September is a busy month: besides Jupiter and Uranus reaching opposition at the same time, Mercury will reach its greatest western elongation, and the Autumnal Equinox and harvest moon will occur.
Mercury will reach its greatest western elongation on September 19. It will rise over an hour before sunrise and should be a great telescope target in the eastern sky into late September. It will appear at its highest and brightest point on the 19th.
The Autumnal Equinox occurs September 22 and the harvest moon follows September 23. The harvest moon is the full moon that occurs closest to the autumnal equinox, called that because its rising time nearly overlaps the setting sun so farmers could continue the harvest into the night hours due to the moon’s light. Since the Autumnal Equinox, when the sun rises due east and sets due west (everywhere except at the poles), is on September 22, the full moon the following night (September 23) is the harvest moon.
Please Note: The above article is made possible by the research and writing of JJ Stamm - Thank you JJ