The September equinox occurs at 20:02 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of fall (autumnal equinox) in the Northern Hemisphere and the first day of spring (vernal equinox) in the Southern Hemisphere.
This September 20, the Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 05:30 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.
This September 12, the planet Mercury reaches greatest western elongation of 17.9 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.
This September 6, the Moon will be located on the opposite side of the Earth as the Sun and its face will be fully illuminated. This phase occurs at 07:03 UTC. This full moon was known by early Native American tribes as the Full Corn Moon because the corn is harvested around this time of year.
This September 5, Neptune will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Neptune. Due to its extreme distance from Earth, it will only appear as a tiny blue dot in all but the most powerful telescopes.
Irene W. Pennington Planetarium 