Caroline’s Rose, also known as NGC 7789, was discovered by Caroline Herschel in 1783. It’s an open cluster in Cassiopeia. Although it’s about the same apparent size as the full moon it is quite a bit dimmer so it takes binoculars to see it.
This is processed to approximate the view trough binoculars or a wide field telescope. In reality there are even more dim stars lurking back there that a more aggressive processing approach would bring out. However, for open clusters, I tend toward the understated approach otherwise the stars feel like they overwhelm the image.
For all the technical details see astrobin.