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Saturday, November 02, 2013


Comet C/2012 S1 ISON brightens,1-8 November 2013

Location of comet C/2012 S1 ISON in the solar system on 1 November. Click to embiggenMorning sky from Friday November 1 to November 8 looking north-east as seen from Adelaide at 5:00 am ACST in South Australia. Comet C/2012 S1 ISON is to the right of  Mars. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Comet C/2012 S1 ISON has now been reported to be (just) visible in 10x50 binouclars. Currently somewhere around magnitude 8, with the Moon gone from the morning sky it visible in small scopes and strong binoculars. In binoculars it should look like a faint, fuzzy dot. However,  its fuzzy, diffuse nature, its closeness to the horizon (between 7 -12 degrees depending on where you are, except Darwin and Far North Queensland, where it is more like 20 degrees above the horizon see here for charts illustrating the difference at different sites)  means that it can be difficult to spot visually in smaller scopes.

If all goes well by  the 8th it should be magnitude 7, and easily seen in binoculars.

The comet is to the right of Mars, making finding it relatively easy. The best time to look for it is when it is highest in the sky and the sky is darkest.  However, especially in the Southern States, because it never gets very high, the best time to look is astronomical twilight. Astronomical twilight is an hour and a half before local sunrise.
On November 1 the comet is in the constellation of Leo, and is just crossing Earth's Orbit (see image above). At this time comet ISON is just under a hand span above the horizon as seen from the latitude of Melbourne, just over a hand span as seen from the latitude of Sydney, nearly two hand spans as seen from the latitude of Brisbane and almost 4 hand spans as seen from the latitude of Darwin. A hand-span is the distance across your knuckles when your hand is outstreached at the end of your arm as if making a "stop" sign.

On the 1st there are no bright stars near the comet. However, bright Mars is nearby and very obvious. If you start at orange Mars and sweep down diagonally to the right (east) of Mars around a hand span (the distance across the palm of your hand as you hold it out at arm’s length like you are making a stop sign), the first brightish star you come to is Chi (χ) Leo, down another 4 finger widths is the next bright star, Sigma (σ) Leo (see the black and white printable map or the PDF map for this to be clearer). 

The comet is roughly in between them, you may need to hunt back and forth a bit to find it.

Over the next few days the comet approaches, then passes, Sigma Leonis, being closest on the 3rd. Sweeping down again diagonally a little over a hand span from Sigma Leonis is the bright star Zanijava, Beta (β) Virginis. The comet approaches beta Virginis and is closest on the 7th and 8th of November. The comet should, all things going well, be easily visible in binoculars now.

A printable PDF map is here.

A black and white map suitable for printing for use with binoculars and telescopes. The large circle is the approximate field of view of 10x50 binoculars, the medium circle the approximate field of view of a 24 mm eyepiece for a reflecting telescope and the small circle a 12 mm eyepiece for a reflecting telescope.Time is astronomical twilight.Click to embiggen. The image is the same orientation as the horizon animation above. Click to embiggenA high power stellarium view of the region around Mars with ISON to go with the black and white spotters map. This view is on the 3rd when the comet is close to Sigma Leonis. Click to embiggen.

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