Brian, after having sent the e-mail I began to wonder if Castors orbit was know and I was looking at dated (both separations) data. So, this afternoon, after reading your e-mail, I checked Brian Workman's binary star calculator for Castor AB. Their separation for 2007 is 4.58" in a PA of 61.95 deg. This is more consistent with what I would have expected. Checking notes from my old 8" f6 Newtonian it wasn't split in 1981, with a 2.38" separation, but was in 1983, with a 2.52" separation, both from the back yard. The latter observation the better night of the two. If anyone is interested in downloading Brian's binary star calculator go to http://www.saguaroastro.org/content/downloads.htm scroll down to and select the Binary Star Calculator. This (third) version is an Excel spread sheet that includes the "Sixth Catalog of Orbits of Visual Binary Stars" by William I. Hartkopf & Brian D. Mason. Clear skies, aj ---- Brian Skiff <bas@xxxxxxxxxx> wrote: > >> Castor...The Orion hand controller gave a separation of 1.8", > >> but the SAC double star database gives 2.2". > > Somebody needs to do some updating of files. The current specs > for Castor (from the USNO double-star site) is 4".4 in pa 59 deg. > > Good test doubles for 8-inches aperture would be in the range > between 1" down to 0".6 (the Rayleigh limit). Have a look at my > "seeing test" list at: > > ftp://ftp.lowell.edu/pub/bas/dbls.dat > > A nice one for this time of year is the pair immediately east of > Procyon, ADS 6263, which is now a bit under 0".9. Really easy to > find. Another one that gets closer to the zenith is ADS 7307, > presently at 1".0. > > > Brian > -- > See message header for info on list archives or unsubscribing, and please > send personal replies to the author, not the list. > -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.