One of my areas of interest in astronomy is the study of planetary nebulae (hereafter PN or PNs). The name is a historical artifact, reflecting that in the telescopes of the late 18th century these various of these objects looked round and pale green in colour similar to Uranus in appearance. ... A collection of pictures of PNs is available at Bruce Balick's Planetary Nebula Image Calalogue page . ... The very nice HST image of the Ring Nebula below is a case in point. ...