September Moon & Planet data for 2013


The Solar System in September 2013

Phases of the Moon (times as shown by guide)

New moon:      September  5 at 11.36 pm NZST (       11:36 UT)
First quarter: September 13 at  5.08 am NZST (Sep 12,17:08 UT)
Full moon:     September 19 at 11.13 pm NZST (       11:13 UT)
Last quarter   September 27 at  3.55 pm NZST (       03:55 UT)

The Southern spring equinox is on September 23 at 8.45 am (Sep 22, 20:45 UT)

NZ Daylight Time, NZDT, commences this year on Sunday 29 September. NZDT will be 13 hours ahead of UT.

The Planets in September

Mercury is at its evening best in the second part of September with Venus shining brightly to its upper right. The latter passes both Spica and Saturn during the month.

In the morning Jupiter emerges further from the Sun but will still be fairly low as seen from mid southern hemisphere latitudes. Mars remains low in the dawn sky as it only slowly distances itself from the Sun.

Planets in the Evening Sky: Mercury, Venus and Saturn.

MERCURY sets about 30 minutes after the Sun at the beginning of September, making it almost impossible to see despite its -1.1 magnitude. Its visibility increases quite rapidly during September even though the planet gets a little less bright. By the 8th it will be about 3° up 40 minutes after sunset at magnitude -0.6. By mid September its altitude 40 minutes after sunset is 7° at mag -0.3, so now getting fairly easy to see. On the 22nd, altitude 10.5°, mag -0.2 and at the end of the month 17° at -0.1, so by then Mercury will be an easy object to the west as the glow from the setting Sun diminishes. At the end of September, following the start of NZDT it will be after 9.30 pm before Mercury sets.

On the 25th, Mercury will be alongside Spica, the star being to the left of Mercury and less than a degree from the planet. The two will form a fine pair, with the planet over a magnitude brighter.

VENUS will set around 9.30 pm, over 3 hours later than the Sun on the 1st as seen from much of New Zealand. It starts the month 6° directly below Spica. On the 6th the planet will be 1.6° to the right of the star. Two evenings later Spica, Venus, the crescent moon, 15% lit, and Saturn will form an ascending line in the western sky.

Ten evenings later again, on the 18th Saturn will be 3.5° to the right of Venus. The following evening Venus will have moved up a little so that Saturn is a similar distance to the lower right of Venus.

By the end of the month, after the start of NZDT, Venus will not set until about 11.30 pm. By then it will be some 12° above Saturn.

SATURN itself sets almost 5 hours after the Sun on September 1, reducing to about two and three-quarter hours on the 30th. At magnitude 0.7 it is a bright object but almost 5 magnitudes fainter than Venus. It will also be outshone by Mercury.

JUPITER and MARS in the morning sky.

JUPITER moves further into the morning sky during September. On the 1st it will rise some 2 hours and 40 minutes before the Sun. 40 minutes before sunrise it will shine brightly but be fairly low to the north of northeast. On that morning the crescent moon, 20% lit, will be 4° to the upper right of the planet.

The moon joins Jupiter again near the end of September. On the morning of the 28th the 45% lit moon will be 8° to Jupiter upper left. The following morning, now 35% lit, the moon is 6.5° to the upper right of the planet. The increase in the percentage of the moon lit at conjunctions at the beginning and end of September is an indication of the increasing elongation of the planet from the Sun.

By the end of September Jupiter will rise soon after 3.30 am NZDT.

MARS, by contrast does not move much further from the Sun during the month. On the 1st it rises about 90 minutes before the Sun, on the 30th 100 minutes earlier. Its magnitude will be 1.6 throughout September.

The moon passes Mars early in September. On the morning of the 1st the 14% lit moon will be some 7.5° above Mars, the following morning it, now 7% lit, it will be 6° to the right of Mars. The planet will be low, 45 minutes before sunrise only 6° above the horizon to the northeast.

Outer Planets

URANUS rises mid evening at the beginning of September and just after sunset at the end of the month. The planet is in Pisces at magnitude 5.7. It is at opposition early in October. Uranus will be 3.5° to the upper right of the almost full moon near midnight on the 20th.

NEPTUNE transits and so is highest soon after midnight at the beginning of September and 2 hours earlier by the 30th. The planet is in Aquarius at magnitude 7.8. Neptune will be some 7.5° to the upper right of the 95% lit moon on the 17th

Brighter Asteroids:

Both (1) Ceres and (4) Vesta were at conjunction with the Sun during August. As a result in September they will be rising shortly before the Sun. By the end of the month their elongation from the Sun will still be less than 30°. Both asteroids are in Leo, Ceres at magnitude 8.6 to 8.7, Vesta 8.2 to 8.3.

(2) Pallas is in Monoceros, magnitude 9.1 to 9.0, changing little during the month

(7) Iris is in Aquarius and fades a little during September from magnitude 8.2 to 8.8.

(324) Bamberga is at opposition in Pisces on September 13. It will then be at magnitude 8.1 making it the brightest asteroid for a night or two. With Vesta rather close to the Sun, Bamberga will in fact the brightest easily observable asteroid for much of the month. It starts September at 8.4 and ends the month at 8.5


Events Diary

The follwing table lists various solar system object events during September. A list of astronomical terms used in may be found after the table.

September 4 Regulus 5.2 degrees north of the Moon
September 5 Moon new
September 6 Venus 1.6 degrees north of Spica
Mercury 4.5 degrees north of the Moon
September 8 Spica 0.7 degrees south of the Moon Occn
Venus 0.5 degrees north of the Moon Occn
September 9 Saturn 2.3 degrees north of the Moon
September 12 Moon first quarter
Moon southern most declination (-19.7 degrees)
September 14 Pluto 1.4 degrees south of the Moon
September 15 Moon at perigee
September 17 Neptune 5.3 degrees south of the Moon
September 18 Venus 3.5 degrees south of Saturn
September 19 Moon full
September 20 Pluto stationary
Uranus 3.1 degrees south of the Moon
September 22 Equinox
September 25 Mercury 0.7 degrees north of Spica
Aldebaran 2.8 degrees south of the Moon
September 26 Moon northern most declination (19.6 degrees)
September 27 Moon last quarter
Moon at apogee
September 28 Jupiter 4.8 degrees north of the Moon
  • apogee: Furtherest point in the orbit of a body orbiting the Earth
  • declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
  • perigee: Nearest point in the orbit of a body orbiting the Earth