The night sky in September 2016

posted 31 Aug 2016, 02:00 by Pete Collins   [ updated 31 Aug 2016, 02:04 ]
by Anne Holt

​Sunset   1st:  19.58    30th:  18.47

New Moon  1st    Full Moon  (Harvest Moon)  16th  

Highlights

The main events for us this month aren't in the sky, they are down here on Earth - our Open day on Sunday Sept 25th and the start of our new season the following Thursday, 29th.  On this day the sun sets at 18.50 and astronomical darkness begins at 20.47 - a whole 13 minutes before we have to pack up and go home.

The Autumnal Equinox, when the sun crosses the celestial equator, is at 15.21 on 22nd.  However, in Manchester the day and night are not of equal length on this, or any other, date.  The nearest it gets is Sept 25th, with a day length of 11hrs 58 minutes and 47 seconds.

There is a Lunar occultation of Neptune on 15th - see 'Planets' for details -  and the following day a penumbral Lunar eclipse.  The moon only passes through the outer part of the Earth's shadow meaning it will be only slightly less bright than ususl.  It starts at 17.54, while the moon is still below the horizon, and ends at 21.54.   You probably won't notice any difference.

Constellations

The Milky Way in still prominent overhead, albeit not in these parts! Find a dark sky site though, and it's spectacular.

Milky Way & Summer Triangle from Derbyshire

The Summer Triangle is high in the southern sky for much of the night in early September.  By month end Aquila is setting in the west at about 2am, with Lyra and Cygnus following just before dawn.

However, on the opposite side of the sky, the Pleiades are climbing above the horizon in the east by 10.30pm at the start of September, and as darkness falls at month end. Capella, in Auriga, and the V shaped Hyades cluster at the head of Taurus the Bull are not far behind.

If you stay up until about 4am (or get up very early) you might see Orion making a welcome return to the night sky.  By the end of September, it should be above the horizon by 2am.

The ecliptic is now slightly higher across the Eastern sky, passing through Capricorn, Aquarius and Aries - though none of these are particularly bright or memorable.

Pegasus, Perseus and Andromeda are still well placed, rising in the east to north east from mid evening, as is the bright W asterism of Cassiopeia higher in the north east.


Planets

Another poor month for seeing naked eye planets, however the two outer ice giants are very well placed for telescopic observation.

Mercury In Virgo, moving into Leo on 8th. Not easily seen for most of the month.  It is at inferior conjunction on 13th, after which it becomes a morning object. It reaches greatest Western elongation on 28th but remains very low in the sky before sunrise. Just before dawn on 29th it is 2 degrees from the 2% lit waxing moon, moving even closer as it gets light - only 1 degree apart at 10am.

Venus In Virgo mag -3.9. Another planet which is hardly visible during September.  Despite its brightness and the fact that it sets at least an hour after the sun, the angle of the ecliptic at this time of year means that it remains too close to the horizon to be easily seen. On 3rd it is 3 degrees from the 5% lit moon.

Mars In Scorpio moving into Ophiuchus on 3rd,  mag -0.3. At the start of the month it sets around 22.30. Because it is currently retrograde - moving westwards against the background stars - it sets in the west only half an hour earlier at month end. By this time it will have moved into Sagittarius and be slightly dimmer at mag 0.1.

Jupiter In Virgo,  mag -1.7. May just be visible, very low in the West, soon after sunset at the start of September.  By  the end it won't be visible as it sets around the same time as the sun.

Saturn In Ophiuchus, mag 0.5. Another one which is difficult to spot in September. At the start of the month it sets around 11pm and may be visible low in the South West after sunset.  On 1st it forms an equilateral triangle with Mars and Antares and on 8th is 3 degrees South of the 43% lit moon, very low in the South West, at around 21.45.  By month end it sets at 21.00 and is too low to be seen by the time the sky begins to darken.

Uranus In Pisces,  mag 5.7. Well placed again in September, rising at 21.00 at the beginning of the month, a couple of hours earlier by the end.  Still theoretically visible with the naked eye but best seen through a telescope.  Even a small one will show the greenish blue disc.

Neptune In Aquarius,  mag 7.8. Easily visible throughout September - if you are looking through a reasonable size telescope. Reaches opposition on 7th and is above the horizon all  night, rising at sunset on 1st and while the sky is still light at month end. On 15th it is occulted by the almost full Moon. It  passes behind the Moon in daylight but it will be reasonably dark when it reappears at 20.55.

For full details of planetary positions on any day see
https://in-the-sky.org/ephemeris.php

Meteor Showers

No major showers this month but September is the peak time for sporadic activity.

Minor showers

Alpha Aurigids.
Active until 10th. Most sources give the peak as Aug 31st but some say Sept 1st.   ZHR 5. (ZHR is zenithal hourly rate - the maximum number of meteors you could expect to see per hour under ideal conditions. In practice, from a suburban location and less than ideal conditions, you can expect to see less than half this number).

September Perseids: 
Active 5th -21st  Peak 9th.  ZHR 5-9
Usually a very faint shower but it occasionally puts on a much better show - though this is not predicted to happen again until 2040.

Beta Cassiopeids. Peak Sept 1st - 6th. That's all I could find out about this one.

Piscids.  Active August 12th to October 2nd.  Some sources say that this shower has a plateau, from Sept 9th to 21st, rather than a peak. Others think it may be 2 separate showers, one peaking at the start of this period, the other at the end.

Southern Taurids. Active in late September, though the peak is not until early October.   This shower often produces some very bright fireballs.

The Piscids and SouthernTaurids are now usually classed as part of the Autumn Antihelion Source.  This consists of several weak showers witn radiants on the ecliptic, opposite the position of the Sun.






 


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