Jupiter will dominate the evening sky to the east and north. Saturn, in conjunction with the Sun early in September will not be visible .
Orbital diagrams for the inner planets December 2007 to March 2008, April to July 2008, July to November 2008 and the outer planets for 2008.
| Date (NZDT) | Diary of Solar System Events in September 2008 for New Zealand |
| September 2 | 6% lit crescent Moon in a close group with Mars, Mercury and Venus, early evening sky. |
| September 3 | 13% lit Moon 2.5° to left of star Spica, magnitude 1.1. |
| September 4 | Saturn in conjunction with the Sun. |
| September 7 | Early afternoon occultation of Antares by the Moon visible from all of New Zealand, and late morning in East Australia.
48% lit Moon 2° from the star in the early evening sky. |
| September 8 | Moon at first quarter 2:04 am NZST (Sep 7, 14:04 UT). Moon at apogee, its greatest distance from the Earth for the Lunar month, 404213 km. |
| September 8 | Jupiter stationary. |
| September 9 & 10 | Jupiter 6° from Moon. |
| September 11 | Mercury at greatest elongation, 27° east of Sun. |
| September 12 & 21 | Venus 19 arc-minutes to right of Mars, early evening sky. |
| September 13 | Uranus at opposition. |
| September 13 | Near full Moon 4° below Neptune. |
| September 15 | Full Moon at 9:13 pm NZST (09:13 UT), just over 5° from Uranus. |
| September 19 | Spica, magnitude 1.1, 2.4 ° from Venus and 2.8° from Mercury, early evening sky. |
| September 20 | Moon at perigee, its closest to the Earth for the Lunar month, 368890 km.
Moon at last quarter 5:05 pm NZST (05:05 UT). |
| September 23 | Southern spring equinox. Sun crosses equator moving south shortly before 4 am. |
| September 23 | Mercury 2° from Spica and 4° from Mars, low early evening sky. |
| September 24 | Mercury stationary. |
| September 28 | New Zealand Daylight Time (NZDT) starts. NZDT is 13 hours ahead of Universal Time, UT. |
| September 29 | New Moon at 9:12 pm NZDT (08:12 UT). |
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MERCURY has its best evening appearance of the year during September. At the beginning of September Mercury will set more than two hours after the Sun, and shine brightly at magnitude 0. As a result it will be easy to see fairly low to the west, as the sky begins to darken after sunset. During the first half of the month its brightness will change little and it will get slightly higher in the sky. Finding the planet will be made easier due to the proximity to Venus and Mars for most of the month.
For the first half of September, Mercury will be above and to the left of Venus as they both move to the east away from the Sun. Mercury will reach its greatest elongation 27° from the Sun on September 11 when it will set about 2 hours and 20 minutes later. After that its easterly motion will slow so that by September 20 Venus will pass it. On September 24, Mercury will be stationary and then start moving to the west, back towards the Sun which itself moves east through the stars. So Mercury will then quite rapidly close in on the Sun and get lower in the evening sky. At the same time it will quickly lose brightness and become lost in the evening twilight by the end of the month.
VENUS will set about 15 minutes before Mercury on September 1, but will gradually set later throughout the month. By September 30 it will set more than two and a half hours after the Sun. Brilliant Venus will act as an obvious marker for the fainter Mars and Mercury throughout the month.
During September Venus will pass Mars at a distance of 19 arc minutes, two-thirds of the diameter of the full Moon, on the 12th. It will be at its closest to Mercury on the 14th and 15th, the two being just over 3.5° apart, although Mars will still be closer than that to Venus. Spica will be just under 2.5° from Venus on the 19th. Throughout this period Venus will be less than 5° from the other planets.
By the end of September Venus will be just over 10° above Mars, with Spica and Mercury lower still.
MARS will be moving to the east throughout September, but not as fast as the Sun. As a result it steadily sets earlier as September progresses, about two and a half hours after the Sun on September 1, and an hour and forty minutes after at the end of the month. Its magnitude will remain virtually constant at 1.7, so it will be fainter than Mercury until the last three days of the month. By then it both planets will be difficult objects in the evening twilight.
Mars will be at its closest to Mercury, with the two 2.6° apart, on September 8. Then Venus passes very close to Mars on September 12. On September 23 Mars passes a now almost stationary Mercury again, this time at a distance of 4.1° and two days later Mars passes Spica, with the two 2.3° apart. Mercury will be the same distance away from, and on the other side of, Spica and a similar magnitude to the star. Spica remains between the two planets for the next few nights, but they are likely to be completely in the evening twilight.
JUPITER will be the dominant object of the mid and late evening sky, once Venus has set. Early in the month Jupiter will be high to the north east early evening, swinging round to the north and at its highest before 9 pm. By the end of the month it will be at its highest by 7 pm. As it doesn't set until some hours after midnight during September, Jupiter will be readily observable all evening.
Jupiter remains in Sagittarius throughout September. The planet is stationary on September 8, so shows little movement during the month, being just over 3° from the 2nd magnitude star Nunki, σ Sgr.
On both the 9th and 10th of September, Jupiter is about 6° from the Moon as seen from New Zealand. (In between time, while Jupiter is set, they get to be only 2.7° apart.) The Moon will be 67% lit on the 9th and 76% lit on the 10th.
SATURN is in conjunction with the Sun on September 4. After this it will start rising before the Sun into the morning twilight. The planet remains close to the Sun throughout September. By the end of the month it will rise just over half an hour before the Sun, so will be virtually unobservable.