The closest full moon of the year is on the 18th of this month. And it happens with a partial eclipse. On its way, the moon starts the month as a waning crescent near Mercury in the morning sky. On the 2nd, an even thinner crescent is near Regulus. Seeing the moon may not be hard, but spotting the star next to it could be a challenge aided with binoculars. On the 2nd, the moon’s new. Then a young moon goes south across the equator on the 3rd and reaches apogee on the 4th when it appears next to Venus in the evening sky. Apogee distance this month is 406,200 km.
The moon passes by Spica on the 6th. Nigeria and Niger are placed well for seeing an occultation. Another occultation happens on the 10th when the nearly first quarter moon meets Antares. Western Australia, part of South Australia, and the Indian Ocean near the Australian continent are in the visibility zone. First quarter is the next day, followed by southern lunistice on the 12th. Note how far south the moon appears. It will get about so far again a few more times before its monthly extremes lessen. Then the moon’s declination won’t be so far from the equator again for 18.6 years. Declination for this event is 28.7°.
The moon’s almost full when it passes Saturn on the 17th. For observers along a wide path from eastern Australia and New Guinea, across the Pacific Ocean over Hawaii, and to the western coast of North America, the moon occults the planet. The time of the central conjunction is 10:22 on the 17th Universal Time. Convert that to your local time zone to figure out if that’s on the 16th or 17th where you are.
The moon is close to the equator going north when it reaches full phase at about 357,500 km away. The aforementioned eclipse takes the northwestern part of the lunar disk into the darkest part of Earth’s shadow. Just 9% of the moon’s disk passes into the umbral cone. Critical times are: 0:41 for the start of the penumbral phase, 2:13 for the partial phase beginning, 2:44 for the moment of maximum eclipse, 3:16 for partial phase ending, and 4:47 for the penumbral phase ending. In local times, for Africa, Europe, and western Asia, it will be a Wednesday morning event. For the Americas, it will happen on Tuesday evening.
This month’s lunar perigee is a few hours after the eclipse at 357,200 km. This month’s and next’s are the two closest perigees of the year. The moon also passes near Neptune on the 18th. It’s a waning gibbous moon near Uranus and then the Pleiades on the 22nd. Then the moon’s near Jupiter on the 23rd. Last quarter happens with northern lunistice on the 24th. Like the southern lunistice earlier in the month, this one happens 28.7° from the equator and is about as far north as the moon can ever get.
See the waning crescent near Mars on the 25th, Pollux on the 26th, and Regulus on the 29th. The moon is nearly new as the month ends.
There’s planet watching to be enjoyed any time of night. Venus passes alongside Virgo in the evening sky this month. The planet passes by Zaniah on the 2nd. The moon passes by the planet from the 4th to the 5th. Venus continues eastward, passing near Porrima on the 6th. Venus is heading for its close encounter with Spica around the 17th. In the last week of September, the planet is clearly on its way out of Virgo and heading toward Libra. Northern hemisphere observers see Venus kind of low above the horizon all month. The view is better from the equator and southern hemisphere, where the planet rises higher into the sky at nightfall.
Saturn’s at opposition on the 8th. Look in a telescope before and after and you may be able to see the shadow the gas ball casts on the rings move from one side to the other. The planet’s 8.67 astronomical units away for this opposition. Saturn continues retrograde motion in eastern Aquarius all month.
Jupiter and Mars continue their eastward motion in the morning. The red planet is faster and is pulling away from the big planet since last month’s conjunction. While Jupiter makes slow progress away from the Hyades V, Mars passes half way through Gemini this month. See the planet near Castor’s feet in the second week of September.
The best chance to see Mercury and be sure of it without a telescope view may be on the 1st when the moon is left of it in the morning. The planet climbs to greatest elongation 18.1° west of the sun on the 5th. Its direct motion takes it near Regulus on the 9th. As the month progresses, the messenger planet gets harder to see in the morning light. It heads into superior conjunction in early October.
Mercury is at perihelion on the 9th.
The September equinox is on the 22nd at 12:44 UT.
You can try to see the Daytime Sextantid meteor shower in the last days of this month. You’ll have to look before and during dawn. While there may be up to five meteors per hour, you likely won’t see but the brightest standing out against the morning light. The radiant point is up mainly during the daytime, hence the shower’s name.