Flamsteed Astronomy Society

September 15, 2014

Sky this Month: September 2014

by Mike Meynell

The autumn equinox is on September 23 – the point where the hours of night and day are equal, so we’re looking forward to the skies getting darker again. I’m going to cover the Moon and the planets and then move on to some of the other objects that you can view in the night sky, even from London. But, first of all, I’m going to start with a quick review of the Perseids meteor shower.

On 13 August, we ran a Perseids meteor watch session in Cudham and we had around 20 members turn up for a very enjoyable evening. The Moon was a real problem this year. It was almost like daylight at times, with our shadows well defined on the ground. One bonus was that, unlike last year, it was possible to see who you were talking to without relying on recognizing their voice! However, it meant that we could only see the very bright meteors. I only saw around 6 or 7 before the clouds got really heavy, but it was still a fun event. The one meteor that I managed to pick up photographically can be seen here.

To give you an idea of the observing problems, here is a time-lapse of the skies over Cudham from around 11pm to 12.30am. You can see the light from the Moon increasing on the left hand side of the image, and then increasing amounts of cloud as the session went on… before we were completely clouded out at about half-past midnight.

However, Sumitra had a bit more luck on the previous evening. Here, you can see a composite image of the brightest meteors that she caught. She used layers and manually aligned the stars (due to the rotation of the earth) and revealed the meteors on a chosen base layer. The ISS can be seen top right. This image was picked up by the Washington Post and displayed on their website!

Background sporadic meteor activity is quite high during September, but there are no major meteor showers active. Watch out for the Orionids around 21-24 October, which coincides with the New Moon, so you may pick up a few. The zenith hourly rate is only around a third or a quarter that of the Perseids, but with the Moon out of the way, it’s quite likely that you will see quite a few.

There is a nice early morning comet on display at the moment – Comet C/2012 K1 PANSTARRS. You should be able to see this low in the east using a pair of binoculars. This comet reached perihelion on 27 August and should be around magnitude +6 from now until the end of the month. The easiest way to find it is to find Jupiter first, then look below and right of the planet for the head of Hydra, and then you should be able to see the comet below Hydra’s head.

The Moon is, of course, always a fantastic object to view in the night sky. This month, the phases of the Moon are as follows:

• Last Quarter: 16 September: 02h (UT)
• New Moon: 24 September: 06h
• First Quarter: 1 October: 20h
• Full Moon: 8 October: 11h

The best times to view the Moon are for a few days around the two ‘quarters’ so that the shadows highlight surface features. Beware, the Moon is very bright. To see it at its best, it’s often better to put a neutral density filter on your telescope eyepiece or, view the Moon before the sky is completely dark (observing in a blue sky helps to kill some of the glare). Low magnification of around 50x will usually show you the whole Moon, but try looking at the Moon with high magnification to really see detail on the surface.

As regards the planets this month:

• Venus is very low in the east and is hard to see due to the proximity of the Sun. Similarly, Mercury is low in the west after sunset and is very difficult to see.
• Saturn is also very low in the southwest following sunset and Mars is a fading evening object, also low in the southwest.
• But, Jupiter is coming back in our skies. Currently an early morning object, you will see it in the constellation of Cancer, rising at about 3am.
• Uranus is at opposition next month. Look south-east in Pisces at around midnight.
• Neptune is still well placed after opposition last month and can be found in Aquarius, due south at around midnight.

This is a beautiful picture of the Milky Way, taken by Sumitra, by the windmill in Rottingdean… close to the light-polluted skies of Brighton. It does show what it’s possible to capture using relatively mid-range DSLRs nowadays. There are lots of discussions and tips on the forum on how you can capture an image like this, so go and take a look. The Milky Way runs from around the north-east to the south-west at this time of year and it’s well worth trying to see if you can get an image.

I wanted to highlight (or perhaps lowlight is more appropriate) a feature of the Milky Way which doesn’t get much attention. Dark Nebulae. A dark nebula or absorption nebula is a type of interstellar cloud that is so dense it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. Edward Emerson Barnard, the famous American astronomer active in the late 19th and early 20th century, produced a photographic atlas of the Milky Way.

A byproduct of his efforts was a catalog of dark nebulae, which are given “B” numbers, so B142 and B143 are together known as Barnard’s E, and can be seen clearly in this image. It’s called “Barnard’s E” because of it’s resemblance to the letter E! You do need a reasonably dark sky to view these features, but, as this is such a large feature, 10×50 binoculars are probably all the magnification that you will need. More magnification will constrict the field of view to much to include the nebula and the surrounding Milky Way to let the feature really stand out. It’s easy to find, as long as your skies are dark enough! Find Altair, the brightest star in the constellation of Aquila – this is the “bottom” star of the Summer Triangle. Train your 10×50 binoculars on this area and look for a pair of elongated blobs with a vague vertical protrusion. At higher magnifications, even 15 times instead of 10, you may find it difficult to pick up.

Finally, I’ll finish with an old favourite for this time of year… Andromeda is an enormous object in the sky – six times the size of the Full Moon, but only the bright central region is visible to the naked eye.

It is quite easy to find. From the left (eastern-most) corner of the great square of Pegasus (high is the south east at around 11pm_, you will see 3 bright stars in a line, all about the same brightness (Alpheratz, Mirach and Almach). From the middle star (Mirach) move up to Mu Andromedae and the same distance again takes you to M31. Almach, incidentally, is one of the nicest double stars in the sky – well worth a look. One of the stars is a golden yellow (the brighter star) whilst the other is blue.

Check out a video of this presentation here.

Posted under: Flamsteed, Sky This Month