| September is the ninth month in the Gregorian calendar and consists of 30 days. The name of September is derived from the Latin ’septem’ meaning seven. September was the seventh month when the year used to start on March 1. |
Autumn begins on September 22nd, when the Autumnal Equinox occurs. The Autumnal Equinox occurs when the tilt of the Earth is in tangent with the orbit of Earth around the Sun. This point marks the beginning of Autumn. An Equinox has an equal amount of daylight and nighttime.
The New Moon for September occurs on Wednesday, September 8th, which will make the weekends of September 4-5 and September 11-12 good times for dark sky observing.
The Full Moon for September occurs on September 21st, the day before the Autumnal Equinox. Since this Full Moon is the closest full moon to the equinox it is the Harvest Moon and the following full moon on October 22nd is then the Hunter’s Moon.
Mercury re-emerges into the morning hours from the sunrise around September 11th, ends it’s retrograde motion and by September 19th reaches its best position for morning observation when it reaches its Greatest Western Elongation.
| On September 19th, Mercury will be 17°52’ from the Sun and rise 1 hour, 12 minutes before sunrise. |  |
Mercury starts September located in the constellation Sextans (The Sextant) and as it emerges into the morning of September 11th, crosses into the constellation Leo (The Lion). Finally, on September 29th, Mercury moves into the constellation Virgo (The Maiden).
Venus is still the Evening Star this month and begins September in the constellation Virgo (The Maiden) and on September 24th crosses into the constellation Libra (The Balance).
Venus begins this month a mere 1°20’ from the Star Spica and less
than 4°30’ from Mars.
On September 11th, the waxing, crescent Moon passes less
than 0°30’ from Venus.
Mars is observable in the evening this month. At the start of September, Mars sets around 8:05 pm (PDT) and by the end of the month Mars sets around 7:05 pm (PDT).
Mars starts September in the constellation Virgo (The Maiden), and by the end of month, Mars sets around 7:05 pm (PDT).
On September 5th, Mars is a mere 2° from the star Spica.
On September 10th, Venus, Mars, the star Spica and the waxing,
crescent Moon are grouped within 6 to 8° from each other.
Since Jupiter is reaching opposition this month on September 21st, it is in excellent position for observation. Jupiter is up all night and is at it’s closest point to Earth in its orbit. Jupiter can be found in the constellation Pisces (The Fish) for the entire month.
Jupiter is in proximity to the planet Uranus all month and is a great starting point for location Uranus. By September 18th, Jupiter and Uranus are less than 0°50’ from each other and they both reach opposition on the same date, September 21st!
On September 22nd, the Full Moon is within 6° of Jupiter and Uranus,
which may make it difficult to observe Uranus on that night.
Saturn is located in the constellation Virgo (The Maiden) until December 2012 and is visible during the evening hours just after sunset during the first half of September. By September 13th, Saturn is disappearing into the glare of the Sunset.
On September 9th, the waxing, crescent Moon passes within 10° of Saturn.
Since Uranus is reaching opposition this month on September 21st, it is in excellent position for observation. Uranus is up all night and is at it’s closest point to Earth in its orbit. Uranus can be found in the constellation Pisces (The Fish) until May 2012.
Uranus is in proximity to the planet Jupiter all month which is a great starting point for location Uranus. By September 18th, Jupiter and Uranus are less than 0°50’ from each other and they both reach opposition on the same date, September 21st!
On September 22nd, the Full Moon is within 6° of Jupiter and Uranus, which may make it difficult to observe Uranus on that night.
Neptune can be observed in the constellation Capricornus (The Sea Goat) until January 2011. Neptune is observable until the very early morning hours of September. At the start of September Neptune sets around 4:30 am (PDT) and by the end of the month sets around 2:30 am (PDT).
On September 20th the waxing, gibbous Moon passes about 4° from Neptune’s position.
Pluto is located in the constellation Sagittarius (The Archer) until the year 2023. Pluto can be observe during the evening to very early morning hours this month. At the beginning of September Pluto sets around 12:30 am (PDT) and by the end, sets around 10:30 pm (PDT).
| On September 15th, the waxing, gibbous Moon passes within 5°30’ of Pluto. |  |
9/1/2010 Last Quarter Moon
9/1/2010 Venus is less than 1°20′ from the star Spica and less than 4°30′ from Mars
9/5/2010 Mars is less than 2° from the star Spica.
9/8/2010 New Moon
9/9/2010 Waxing, Crescent Moon passes within 10° of Saturn
9/11/2010 Waxing, crescent Moon passes within 0°50′ of Venus
9/14/2010 First Quarter Moon
9/15/2010 Waxing, gibbous Moon less than 5°30′ of Pluto
9/18/2010 Jupiter and Uranus at conjunction within 0°50′
9/19/2010 Mercury reaches its Greastes Western Elongation - Best Morning View (17°52′11″)
9/20/2010 Waxing, gibbous Moon about 4° from Neptune
9/21/2010 Both Jupiter and Uranus reach Opposition
9/22/2010 Fall begins with the Autumnal equinox
9/22/2010 The Full Moon passes less than 6° of Jupiter and Uranus
9/23/2010 Full Harvest Moon
9/30/2010 Last Quarter Moon
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