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:...Lewis (on page 374 of his article in "The Observatory") gives a table of illumination levels at a series of distances from the centre of the disc. The maximum illumination of the first bright ring is given as .017 (relative to 1.000 for the disc centre). That gives a ratio just short of 60:1, or near enough, 4 magnitudes instead of ~2.6 (12:1)...
Quote:... +/- 20mm isn't too bad related to a 140mm aperture - though I'd like to see it closer. Down at the 50mm aperture level that variation tells us nothing useful. It's proportional, as I'm sure you know...
Quote:...Stick that in yer pipe and smoke it...
Quote:Neil, interesting input, though I'm hesitant to credit it at face value - so my thoughts were pretty much in the direction Wilfried has offered. Perhaps I'd have been more inclined to believe the claim if it were, as Wilfried suggests, a 60mm f/15 refractor I hear those things are made by the Harry Potter telescope company, and even muggles can get the use of them - and they outperform anything else you can buy ..... More seriously, diffraction theory doesn't allow for what's claimed. And "theory" as you know is a strong word in science, though a dismissive term in common usage. I'd certainly agree about getting elongation, perhaps notched, with a 4-inch f/15 refractor at 0.9". Of course, we'd need to know that the double in question was at 0.9" at the time of the observation - in case that was an old measure, and the pair had widened by the time of the observation. Ne'ertheless, welcome to the discussion. I'm hoping a few more folk, from wherever, might be "buttin in". So, feel free to offer more miraculous splits. I get the occasional one myself, and with no help from smoking anything nor from "a wee dram" as the Scots would have it. Though I find these miraculous observations more often happen with uneven pairs, where the rules are still uncertain. The even pairs are very law-abiding. And I'm still hunting for the fabled SW Burnham 0.2" double seen with a 6-inch telescope. I'm working my way through his General Catalogue of Doubles (the 1900 version - only his own discoveries). So far, no definite find, though plenty of tough examples. Does anyone know which double it was that keeps being mentioned - without identification? as the 0.2" pair found with the 6-inch.... I have found several cases where Burnham writes along the lines of "thought it was likely double with the 6-inch, but it was single with 18.5-inch and/or 36-inch" - and the star in question is not listed as a double these days in the WDS. Which suggests it was a false impression - indeed, Burnham remarks on this view himself, saying it was the likely explanation in several cases where follow-up observations found no sign of a second star. Working at the limits is tricky.
More seriously, diffraction theory doesn't allow for what's claimed. And "theory" as you know is a strong word in science, though a dismissive term in common usage.
"You're not afraid of the dark, are you?" - Riddick "The best scientists are humble. They seek to understand, not to ensure their legacy, but merely to understand." - Mori
Quote: Using a violet or blue violet filter on many a star would dim it substantially but the diffraction pattern never changes size.