Okay, just a speculation. It is commonly known as "Pickering's Dozen", I forgot to mention. Most probably the 12-point scale you mentioned was his next project (as you say) and he just left it on the back burner too long. Jack > Is this the 12-point Pickering scale you were referring to? It was > devised by W.H. Pickering and has 12 points... maybe he did finish it, > well maybe not. It is a test of visual acuity and goes in increasing > order of difficulty. It's from an article in the June 97 Astronomy (p. > 82) on naked-eye Moon observing! I honestly don't know....I only forwarded text from a fellow in England that happened to be discussing the same topic on a different mailing group. --Thad -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.