IOM April 2011 – the Coma Cluster of galaxies, Abell 1656

Our April Fool’s Day imaging object of the month is Abell 1656, the Coma Galaxy Cluster!  Abell 1656 is a massive cluster of galaxies in the constellation Coma Berenices (Berenice’s Hair) and is over 2-degrees in diameter!  Nearly everything you see in the image below that is not obviously a star is actually a galaxy.  With over 650 galaxies in the cluster, Abell 1656 is one of the densest collections of galaxies in the entire sky.

The giant central elliptical galaxies, NGC 4889 on the left and NGC 4874 on the right, lie some 300 million light years away, and they are both around 250,000 light years in diameter – about two and a half times bigger than our own Milky Way.  Strangely – NGC 4874 is a strong radio source, while NGC 4889 is not.

In the Sky 90 at f#4.5 I prefer to use pretty long subs for faint fuzzies, often around 10-minutes per sub.  With the usual rule of at least 50-subs for a smooth image, this means investing around 8-9 hours total imaging time on this one – but it’s got to be worth it!  Where else are you going to get an image with so many galaxies in a single frame?  Clearly this will be more than one night’s work, and I would suggest that it is probably worth coming back to this one year after year to keep adding more data and detail to this amazing region of space.

Until May – clear skies to you all!

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