Caldwell 1 (The Polarissima Cluster)

I was lucky again with the weather last night as it cleared after a somewhat windy and showery day. In fact the wind dropped completely and at about 11.00pm BST the sky was dark and clear. I again went for an object that was suggested by the Dwarf 3 Atlas and this was Caldwell 1 (the Polarissima Cluster or NGC 188). This open star cluster is actually in the constellation of Cepheus but is very close to the North Celestial Pole and so never rises nor sets. This is what I obtained after 296x15s (1 hour 14 minutes):-

The first frame was taken at 23:13 BST and the last at 00:43 this morning. The astro filter was employed and the gain was 60. Auto parameters were used in Stellar Studio. I have increased the saturation of the image in Photoshop and binned it x2. Here is a close up of the object using the unbinned data:-

At an age of about 7.8 billion years, this is one of oldest open clusters that we know of in our galaxy. In most circumstances a cluster this old would not have survived as a physical unit as it would have been dissolved by the interaction of its members with the disc of the galaxy. However, C1 lies well above the plane and so has survived more or less intact. 

All text and images © Duncan Hale-Sutton 2026