150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
David Cotterell Toronto, Ontario "If an observer actually sees an object, there is no point in referring to a formula to find out whether he ought to see it; and if he fails to detect it, no formula will ensure his success." - W.H. Steavenson 8" f/15.5 TEC Maksutov - 16" f/5 Teeter/Zambuto Dob - TEC 140 - AT 65EDQ APO Refractor - Astro-Physics Mach 1 GTO Mount - iOptron ZEQ25 mount - Discmount DM6 - Canon 60Da
Quote:Round. Elongated. Notched (aka 'peanut' or 'figure 8'). Black sky split. These should be all anyone needs. These 'limits' - Dawes, Sparrow, Rayleigh, Lord - are, for lack of a better term, limiting. And all of them are so full of asterisks - a whole bunch of "it depends". Will someone chose not to observe a pair because it lies below an arbitrary limit? I hope not. Pour on the X's and enjoy. Dave
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote:Will someone chose not to observe a pair because it lies below an arbitrary limit?
Used acronyms: NEML=Naked Eye Magnitude Limit, SQM=Sky Quality Meter, TML=Telescope Magnitude Limit, CO=Central Obstruction, delta_m=difference in magnitudes between double star components, RoT=Rule of Thumb, pD_mm=proposed D_mm for resolving a binary (ident with earlier used pA=proposed Aperture), D_mm=Diameter (of scope) in mm, UCAC4=USNO CCD Astrograph Catalog 4th edition
Quote:You know what it is, Dawes has a specific look that's easier than Abbe. I think its easier to call a Dawes than an Abbe in the field. Yeah so in a real way with reservations a limit is what you make it. I guess that was my point condensed into a sentence.Pete