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Thursday, October 17, 2013


Comet C/2012 S1 ISON meets Mars, 16-23 October 2013

Location of comet C/2012 S1 ISON in the solar system on 16 October. Click to embiggenMorning sky on Friday October 18 looking north-east as seen from Adelaide at 5:30 am ACST in South Australia. Comet C/2012 S1 ISON is below Mars, and visible in amateur telescopes. The inset shows the view of Jupiter through a telescope at this time. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Rumors of Comet C/2012 S1 ISON's demise are greatly exagerated. It is still brightening and looking very nice. Currently it is visible in modest amateur instruments such as 10-12" reflecting telescopes. Currently magnitude 10, It should theoretically be visible in smaller scopes, but its fuzzy, diffuse nature and 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)  means that it is difficult to spot visually in smaller scopes.

The highlight of this week is the comets close encounter with Mars. Comet ISON was actually closest to Mars on October 1, but the orbital geometry means that from Earth it will appear closest on the 18th. Between now and the 23rd though Mars and ISON (and the nearby bright star Regulus) are still close enough for good imaging opportunities (although you can't see it visually, long exposures on varuous imaging systems  will bring it out).  The comet is just below and to the left of Mars, making finding it relatively easy. Over the next few days it is roughly midway between the brightish star 37 Leo and Mars, making it even easier to find.

There have been some great images taken so far of ISON and Mars and Regulus, some with just DSLR's (at really high ISO ratings though). Here's another using a telephoto lens. So it's well worth having a go at imaging it under dark skies (the waxing Moon may be a problem though). Some charts that allow you to find the comet more easily. A printable PDF version 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 reversed and inverted as seen through a telescopeA high power stellarium view of the region around Mars with ISON to go with the black and white spotters map.Unlike the spotters map it is not reversed and inverted as in telescope views. This view is on the 18th. Click to embiggen.

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