Saturday, September 5, 5:54 a.m. EDT
Last Quarter Moon
The Last Quarter Moon rises around 11:30 p.m. and sets around 3 p.m. It is most easily seen just after sunrise in the southern sky.
Sunday, September 13, 2:41 a.m. EDT
The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the East as a narrow crescent a morning or two before, just before sunrise. It is visible low in the West an evening or two after New Moon.
Monday, September 21, 4:59 a.m. EDT
First Quarter Moon
The First Quarter Moon rises around 1:30 p.m. and sets around midnight. It dominates the evening sky.
Sunday, September 27, 10:51 p.m. EDT
The September Full Moon is known as the Harvest Moon or Full Corn Moon. It rises around sunset and sets around sunrise; this is the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky.
Neptune at opposition
Tuesday, September 1, midnight
Neptune will be directly opposite the Sun in the sky, and visible all night. It is located in Aquarius but is too faint to be seen with the unaided eye. Use binoculars and a star chart from Starry Night.
Mercury at greatest elongation east
Thursday and Friday, September 3 and 4, dusk
Mercury will be well placed in the evening sky for observers in the southern hemisphere, less so for observers in the north.
Aldebaran and the Moon
Friday/Saturday, September 4/5, near midnight EDT
Observers on the eastern part of North America with low eastern horizons may be able to see the Moon occult the first magnitude star Aldebaran just after moonrise (around midnight, but check for local times). Observers in Europe will see it just before sunrise on the 5th.
Friday, September 11–Thursday, September 24, before dawn
The best time in the year to see the dim glow of the zodiacal light in the pre-dawn eastern sky, the light reflected from millions of interplanetary particles. It lies along the ecliptic (shown in green).
Partial solar eclipse
Sunday, September 13
This eclipse will be visible from southern Africa, Antarctica, and the oceans in between. Seen here is the maximum eclipse in Cape Town, South Africa.
Wednesday, September 23, 4:21 a.m. EDT
The Sun crosses the celestial equator moving southward, causing the days to grow shorter in the northern hemisphere and longer in the southern hemisphere.
Sunday, September 27, evening
There will be a triple treat for observers in eastern North America as sun, Earth, and moon align: a total lunar eclipse, the moon at its closest, and a full moon, all in one evening. At 8:12 p.m. EDT, the lunar eclipse will begin with the first faint lunar shadow creeping onto the moon. At 9:48, the moon reaches an extreme perigee, the closest it will get to Earth in all of 2015: 221,753 miles (356,877 km). Total phase of the eclipse will begin at 10:11 p.m. and mid eclipse will be at 10:47. At 10:51 it will be the instant of full moon, the largest full moon in 2015. At 11:23, the total phase of the eclipse will end, and at 1:23 a.m. the last of the moon’s shadow will leave the moon. In western North America, the moon will already be in eclipse when the moon rises. Observers in South America, Europe, and Africa will also see most of this eclipse. The illustration shows the moon just entering the umbral shadow of Earth at 9:12 p.m. EDT.
Vesta at opposition
Monday, September 28, 11 p.m. EDT
The brightest asteroid Vesta will be directly opposite the Sun and visible all night in Cetus. At magnitude 6.2, it will be right at the limit of naked-eye visibility, but easily spotted with binoculars.
Mercury is well placed in the evening twilight for the first half of the month. This apparition is more favorable for observers in the Southern Hemisphere.
Venus is now a bright object in the pre-dawn sky, reaching maximum brightness of magnitude –4.8 on the 21st.
Mars is low in the eastern twilight, moving eastward through Cancer into Leo.
Jupiter reappears in the eastern pre-dawn sky in the middle of the month..
Saturn is low in the southwest mid-evening sky, and sets in late evening.
Uranus rises in mid-evening in Pisces, nearing opposition on October 12.
Neptune is in opposition on the 1st, visible all night in the constellation Aquarius.