NGC 7789 is an open cluster in Cassiopeia. It is one of my favorite visual star clusters in my 10" f/5 scope. It is thought to be about 8000 light years distant and about 1.6 billion years old. Its most massive stars have turned to red giants that seem clustered on the western edge of the cluster. The blue A and F stars are still on the main sequence and give rise to the blue color stars that dominate the rest of the cluster. The cluster was discovered by Caroline Herschel on November 1, 1783. It is about 16 minutes of arc across which translates to about 37 light years in diameter at 8000 light years. If there are any inhabitants of a star in the cluster they would have a rather bright starry sky to wonder about with a sky full of Sirius like stars shining down on them along with a few far brighter red giants.

Dreyer's description reads: "Cluster, very large, very rich, very much condensed, stars of 11th to 18th magnitude." I'm not sure I agree with the "very much condensed" however. Sure seems rather even in my image and that agrees with my visual impression in the 10".

14" LX200R @ f/10, L=10x5' RGB=2x10'x3, STL-11000XM, Paramount ME