3 minutes exposure, Meade 416XTE CCD.
300mm f/6 newtonian at prime focus.
Abell 23 is a relatively large, low surface brightness planetary nebula in Puppis. The magnitude is quoted as 13.1, but the light is spread out over and area 54" in diameter. It was not visible in a 12" telescope, and is only weakly recorded in this image, just right of centre.