The long hours of summer daylight are hastening to an end. The effect is more extreme the farther north an observer is. For someone in Miami, Florida, the sun rises at 7:01 a.m. and sets at 7:40 p.m. on September 1, and by September 30, the sun rises at 7:13 a.m. and sets at 7:09 p.m. This amounts to only a 12 minute difference of daylight in the morning and a 31 minute difference in the evening. But for a location such as Minneapolis, Minnesota, the sun rises at 6:36 a.m. and sets at 7:50 p.m. on September 1 and by September 30 the sun rises at 7:10 a.m. (a 34 minute difference) and sets at 6:55 p.m. (a 55 minute difference).
The September Equinox and the Harvest Moon
In the Northern Hemisphere, the September Equinox brings the first day of fall. On the equinox, the sun rises directly in the east and sets directly in the west. The exact moment of equinox for 2010 is September 22, 11:09 p.m. EDT. For locations farther east than the east coast of the United States, the equinox will occur after midnight and therefore autumn begins in these locations one day later, on September 23.
September 23 is also the date of the Harvest Moon, the full moon for the month. The precise moment of full moon is at 5:17 a.m. EDT. Most people first notice the full moon as it rises in the east around sunset. On September 22, the full moon will rise at 99.6% lit, as it moves into full phase, and by moonrise on September 23, the date of the full moon, the moon will actually be farther past its peak of full phase and only appear at 99.4% lit. However, each night the moon will be so full it will seem as if there are two full moons at sunset in September.
Jupiter is the Telescopic Target of the Month
Jupiter shines at peak brilliance for September, with a stunning magnitude -2.94, its maximum possible brightness. The planet reaches opposition, or opposite the sun in our sky, on September 21. On the evening of September 20, Jupiter will lie just 368 million miles from Earth, or 3.95 astronomical units. This measurement means that Jupiter is as close as it will get to Earth for the next 12 years, in September 2022. Jupiter will be the best choice for observing through a telescope all month. It rises in the east at sunset and sets in the west at sunrise. Look for the Great Red Spot, the four orbiting Galilean moons, and the light and dark bands across the planet's surface.
As a bonus, Jupiter is close to the planet Uranus all month. At the beginning of the month, the two planets are 1.7 degrees apart, and by month's end they lie 1.4 degrees apart. On September 18, Jupiter will pass 0.8 degrees south of Uranus. Uranus shines at magnitude 5.73 and will be the closest point of light at this brightness except for Jupiter's four inner moons. This is a great opportunity to see Uranus for observers who have never viewed it before.
The Planets in September
Other than Jupiter and Uranus, the other visible planets this month are in the west as the sun sets. Venus is still dominant and bright at magnitude -4.8, its brightest possible, even though it is stuck near the horizon and bathed in the twilight glow. The planet's shape moves from 41 percent lit to a 19 percent crescent, but it does not dim because its apparent size grows from 1/2 arcminute to 3/4 arcminute across. Venus's window of its brightest apparition is between September 17 and October 4.
Venus lies just a degree from Spica on September 1, with Mars to their right. Over the weekend of September 4-5, Mars and Spica are 2.1 degrees apart. Saturn is disappearing with the sun. For early risers, Mercury makes its best morning appearance of the year the second week of September. Look in the constellation of Leo the Lion near his lower foot star, Rho Leonis. The two objects are 20 arcminutes apart on September 16 and 17.
Source: Celestron's The Sky Software
Kelly Whitt - I have been a professional writer for more than a decade, covering many topics from science-based articles to do-it-yourself home ...
