Galaxy Cluster in Ursa Major
The patch of dim, hazy spots just to the lower left of center in this image is not very impressive in its appearance. What is impressive is its estimated distaance of 2.3 billion light years, making it the most distant galaxy cluster I have imaged. Abell 665 also has the distinction of being the only galaxy cluster in Abell's catalog that has richness class of 5, meaning that the density of the galaxies in this cluster is very high, at least as viewed from our perspective so far away.
I was only able to collect about an hour's worth of light before clouds moved in on the night I took these exposures. Longer exposure times would probably bring out the galaxies in more detail.
Image details: Exposure times of 18 minutes luminance, and 15 minutes each of red, green, and blue, taken with an SBIG ST-8300M imager and a 14" Meade LX850 telescope at f/6.