150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
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
Astronomy educator/Sidewalk astronomer
Owner of Astronomy Delight franchise
18 inch f4.42 Dob on eq platform w ST120 f/5 finder
12 inch Zhumell Dob
8 inch f/6.9 home made Dob with Seevers optics
William Optics red 10th Anniversary 80mm FD
C8 XLT on Vixen GPDX
26lb eyepiece box
Cernan Space Center astronomer
Member of Northwest Suburban Astronomers
Quote:Congratulation, if my current RoT model is any good you managed to split a double at the about 15% split probability range for a 6" refractor - seems to be near the upper limit of what is possible with your scope.
Quote:So you've been able to (just) make it out...
...what you can see without having to spend 30-60 minutes straining to see...
Quote:...(10mm UP HD Ortho 1.6x Barlow) and (262x with 12mm UP HD Ortho and 1.6x Barlow) reversed in the post?
Quote:... my older, simple RoT would give this one as being at the limit for a 6-inch scope, preferably unobstructed. ...
Quote:Alright, another thought on blur size, especially in the presence of some residual SA. At best focus, there is a small halo of blur surrounding the Airy disc. In well corrected or balance conditions, this blur is very weak. However, for pure spherical, unbalanced optics the blur at best focus can be smaller and more intense. APOs and Maks need the balanced form to correct for higher order SA, as I understand it. They use highly curved spherical surfaces which give off lots of high order SA resulting in a small, but compact blur around best focus.
Surely APOs are well balanced, some Maks may or may not be. I /suspect/ mine is balanced to come degree after star testing for that very thing. The result is a broader, less bright blur around best focus. So, maybe the amount of correction, especially in fine APO samples, enables detection of faint, unequal binary stars because the blur intensity is greatly reduced.
I am not sure how blur and diffraction are related, they may be the same thing caused by the longer caustic focus. I think they are not related, however, because even a perfect parabola will have diffraction but no blur at best focus. (Advantage reflector?)