Double Cluster

| 2 images

In between nights imaging Andromeda Galaxy, I also gathered some image data on another naked eye object: The Double Cluster. Also known as Caldwell 14, the Double Cluster is comprised of two open clusters of stars in close visual proximity to each other. The unique designations for the clusters are NGC 869 and NGC 884, or h Persei and X Persei. As their alternative designations indicate, the double cluster is located within the constellation Perseus, just over the border from Cassiopeia. The region is rather dense with stars, as it is still along the outer arms of our home, the Milky Way.

The clusters are about 7200 light years distant, and are comprised of enough stars that in total, they are 20,000 times more massive than our Sun. Both clusters each contain over 300 hot blue super-giants. It is assumed that the clusters are moving towards us, at a speed of about 24 miles per second (which, in cosmic terms, is actually relatively “slow”…128,000 feet per second.) We have man-made objects that orbit the sun (heliospheric imaging satellites) at over 150,000 miles per hour, which is about 42 miles per second or 220,000 feet per second.

The Double Clusters are actually naked eye objects. Under city and suburban skies, you are unlikely to find them, let alone see them even with averted eyes. Under darker rural skies, they can be picked out with the naked eye (better with slight aversion), and show up quite well in a decent pair of binoculars or an amateur telescope. They appear as a slight “fuzzying” of the sky…probably most often mistaken for a very small, light puff of cloud by those who don’t know where to look. As far as finding the clusters, look just south and slightly more east a short distance from Cassiopeia, in the northern most reaches of Perseus.

Technical Details

Total Integration Time: 1hr
Number of Subs: 42
Flat Frames: 30x
Bias Frames: 200x
Exposure per Sub: 100s ISO 200 f/5

Processing Details

Integrated with DeepSkyStacker
Initial processing with PixInsight
Final processing with Photoshop w/ Carboni’s Astronomy Actions

Imaged under Bortle Scale Orange Zone, suburban city light pollution (grayish-orange skies), from my back yard outside of the Denver Metro area.