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Mercury

Mercury reaches greatest elongation east on September 21st when it's positioned 26 degrees east of the Sun, close to the maximum possible obtainable. Unfortunately due to the angle of the ecliptic, the planet is unsuitably placed for observation from northern temperate latitudes this month. However for observers in equatorial and more southerly locations Mercury is superbly placed, visible above the western horizon just after sunset throughout September and into early October. From these latitudes, this also happens to be the most favourable evening apparition of the year.

MESSENGER spacecraft image of Mercury's southern hemisphere (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

For example, on September 1st from latitude 35S (approx. equal to Sydney, Cape Town and Santiago), Mercury will appear 10 degrees above the western horizon 45 minutes after sunset. The planets altitude then increases each subsequent evening, peaking on the day of greatest elongation east at 17 degrees. By months end Mercury is still 14 degrees above the horizon. The diagram below shows the changes in position of Mercury, 45 minutes after sunset from latitudes of 35 degrees south.

Mercury evening apparition as seen from latitudes of 35S, 45 minutes after sunset

During September, the brightness of Mercury fades slightly from magnitude -0.2 to +0.3. On the 21st, the planet passes 0.6 degrees south of Spica (α Vir - mag. +1.0) with the thin waxing crescent Moon 4 degrees south of Mercury on the same day, forming a nice triangle.

Venus

Venus long morning apparition finally comes to an end during September. At the start of the month the planet remains a brilliant object low above the eastern horizon before dawn, shining at magnitude -3.9. However, it's not long before the brightest planet of all is lost to the glare of the Sun. For those at southern latitudes the planet will only be visible for the first week of the month, observers at northern temperate latitudes should be able to catch Venus until at least the middle of the month with those in the tropics possibly able to glimpse the planet for a few more days still.

On September 5th, Venus reaches perihelion at a distant of 0.718 AU (approx. 107 million kilometres or 66.7 million miles) from the Sun. On the same day the planet passes 0.8 degrees north of the Regulus (α Leo - mag +1.4), the brightest star in Leo.

Mars

Mars remains an evening object during September, visible after sunset above the southwestern horizon (NH) / western horizon (SH). The Earth is currently distancing itself from the planet so it continues to fade in brightness (mag. +0.6 to +0.8) and shrink in apparent size (6.8 to 6.1 arc seconds) as the month progresses.

Having overtaken Saturn at the end of last month, the "Red planet" starts September in Libra. It then continues its rapid direct movement against the "fixed" background stars, passing into Scorpius on September 13th before moving into Ophiuchus on September 26th, where it remains for the remainder of the month.

Last month it was interesting to compare the colours of deep orange-red Mars as it passed by creamish white Saturn. This month, another interesting conjunction occurs on September 27th when Mars passes 3 degrees north of red supergiant Antares (α Sco - mag. +1.0), the brightest star in Scorpius. Antares is often referred to as the "Rival of Mars" and the two should appear very similar to the naked eye, although Mars will be marginally brighter at magnitude +0.8.

On September 29th, the waxing crescent Moon passes 3 degrees north of Mars.

Mars and Saturn during September 2014

Mars and Saturn during September 2014 - pdf format

Jupiter

Jupiter. mag. +1.9, is now a brilliant morning object moving direct amongst the stars of Cancer. At the beginning of September, the dominant planet in the Solar System rises over 2 hours before the Sun increasing to over 4 hours by months end.

The planet dominates a relatively barren part of the sky although the twins of Castor (α Gem - mag. +1.6) and Pollux (β Gem - mag. +1.1) are positioned about 20 degrees northwest of Jupiter. Since moving into the morning sky, this is probably the first month when telescope users have enough observing time to study the planet in detail. As the year progresses, Jupiter will continue to brighten and increase in apparent size as it moves towards opposition early next year.

On September 20th, the waning crescent Moon passes 5 degrees south of Jupiter.

Jupiter during September 2014

Jupiter during September 2014 - pdf format

Saturn

Saturn, mag. +0.6, remains an early evening object in Libra throughout the month. On September 1st, the "Ringed planet" appears rather low down above the southwestern horizon from northern temperate latitudes, setting about 2 hours after the Sun. However, it's much better placed from Southern Hemisphere locations, where it appears higher in the sky and sets much later at around midnight.

On the first day of the month, Mars (mag. +0.6) is positioned 5 degrees southeast of Saturn but as its much closer to Earth and traveling on a faster trajectory, it's not long before Mars distances itself from Saturn.

By months end, for northern-based observers Saturn will be rather low down at dusk but better placed and easier to see for observers located further south. On September 28th, the waxing crescent Moon passes 0.7 degrees north of Saturn and an occultation is visible from Hawaii, southwestern Alaska and the Pacific Ocean (4:25 UT).

Uranus

Uranus, mag. +5.7, is now closing in on next month's opposition. The planet is moving slowly retrograde in Pisces and at the start of September rises in the east less than two hours after sunset. The period of visibility continues to improve as the month progresses and by month's end, Uranus is practically visible all night.

A good starting point to find Uranus is the "Great Square of Pegasus". Uranus is positioned about 25 degrees southeast of the centre of the square. The stars ε Psc (mag. +4.3) and δ Psc (mag. +4.4) are positioned 2 degrees northeast and 2 degrees northwest of Uranus respectively.

Uranus has an apparent diameter of 3.7 arc seconds and a small telescope at high magnification will show a small green disk that's obviously non-stellar. However, even when viewed through the largest amateur scopes it's difficult to make out any surface details on Uranus.

On September 11th the waning gibbous Moon passes 1 degree north of Uranus.

Uranus during September 2014

Uranus during September 2014 - pdf format

Neptune

Neptune is located in Aquarius and has recently just past opposition (August 29th). The distant planet is moving very slowly retrograde and remains well placed for observation during September, visible as soon as it's dark enough until just before sunrise. At magnitude +7.8, Neptune is the only planet that can't be glimpsed with the naked eye (under dark skies Uranus can be seen), however it can be spotted relatively easily with binoculars or small telescopes.

The constellation Aquarius lies between the Great Square of Pegasus and the barren starfields of Capricornus and Piscis Austrinus. It contains mostly faint stars but locating Neptune is not difficult once you have identified sigma Aqr (σ Aqr -mag. +4.8). Neptune is positioned about a degree to the north with the planet being 15x fainter than the star.

On September 8th, the almost full Moon passes 5 degrees north of Neptune.

Neptune during September 2014

Neptune during September 2014 - pdf format

Solar System Data Table September 2014

 DateRight AscensionDeclinationApparent MagnitudeApparent SizeIllum. (%)Distance from Earth (AU)Constellation
Sun5th Sep 201410h 54m 14.4s06d 59m 41.6s-26.731.7'1001.008Leo
Sun15th Sep 201411h 30m 11.3s03d 13m 06.8s-26.731.8'1001.006Leo
Sun25th Sep 201412h 06m 04.6s-00d 39m 30.1s-26.731.9'1001.003Virgo
Mercury5th Sep 201412h 13m 37.1s-01d 58m 37.9s-0.105.6"791.205Virgo
Mercury15th Sep 201413h 00m 58.4s-08d 29m 58.0s0.006.2"681.079Virgo
Mercury25th Sep 201413h 38m 12.3s-13d 30m 15.6s0.107.3"530.926Virgo
Venus5th Sep 201410h 05m 54.0s12d 57m 23.4s-3.910.0"971.661Leo
Venus15th Sep 201410h 53m 04.6s08d 35m 05.0s-3.909.9"981.682Leo
Venus25th Sep 201411h 39m 15.0s03d 48m 20.7s-3.909.8"991.698Virgo
Mars5th Sep 201415h 24m 47.8s-20d 05m 21.4s0.706.7"871.396Libra
Mars15th Sep 201415h 52m 09.1s-21d 39m 49.1s0.706.5"881.451Scorpius
Mars25th Sep 201416h 20m 56.7s-22d 59m 21.7s0.806.2"881.504Scorpius
Jupiter5th Sep 201408h 53m 28.6s17d 58m 47.0s-1.832.2"1006.116Cancer
Jupiter15th Sep 201409h 01m 32.4s17d 26m 46.5s-1.932.7"1006.027Cancer
Jupiter25th Sep 201409h 09m 07.0s16d 55m 39.1s-1.933.3"1005.921Cancer
Saturn5th Sep 201415h 05m 00.0s-15d 13m 31.5s0.616.1"10010.300Libra
Saturn15th Sep 201415h 07m 58.9s-15d 27m 57.8s0.615.9"10010.446Libra
Saturn25th Sep 201415h 11m 25.5s-15d 43m 49.9s0.615.7"10010.578Libra
Uranus5th Sep 201400h 58m 18.7s05d 28m 15.3s5.703.7"10019.166Pisces
Uranus15th Sep 201400h 57m 03.2s05d 20m 15.9s5.703.7"10019.088Pisces
Uranus25th Sep 201400h 55m 39.2s05d 11m 27.5s5.703.7"10019.036Pisces
Neptune5th Sep 201422h 31m 28.9s-10d 05m 03.3s7.802.4"10028.970Aquarius
Neptune15th Sep 201422h 30m 28.3s-10d 11m 00.4s7.802.4"10029.006Aquarius
Neptune25th Sep 201422h 29m 31.5s-10d 16m 32.0s7.802.3"10029.070Aquarius