September 2 - 3 - Jupiter Without Moons. The planet Jupiter can usually be seen with all or some of its four largest moons in binoculars and small telescopes. It is very rare for it to be seen otherwise. But late on this night in most of the Western Hemisphere, the planet will be visible with no moons for nearly two hours.
September 4 - Full Moon
September 17- Uranus at Opposition. The blue-green planet will be at its closest approach to Earth. This is the best time to view Uranus, although it will only appear as a tiny blue-green dot in all but the most powerful telescopes.
September 18 - New Moon
September 22 - The Autumnal Equinox occurs in the northern hemisphere at 21:18 UT. There will be equal amounts of day and night. This is also the first day of fall.
September 22 - Close Conjunction of Mercury and Saturn - Early in the morning over North America, the planets Mercury and Saturn will appear in the sky only 0.3 degrees apart.