150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
... and still the best wife I could wish for!
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:I NEVER found it easier to split uneven doubles in those scopes in comparison to a refractor.
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:...do slightly better near the Dawes limit for equal bright doubles up to +6mag because the spurious disk is smaller...
Quote: ...the actual Airy disc itself ... is smaller ...
Quote:Quote: ...the actual Airy disc itself ... is smaller ...
The slightly smaller size of the diffraction pattern due to CO alone seems to have no real impact - the additional reduction of the size of the spurious disk due to the loss of energy seems to have more effect I think.
...outside of this list STF412 (7 Tau) with a req. Ap of 173 - it seems you have a tendency to overperform
Quote:Hi John,Sorry, I didn't mean to put words in you mouth or imply you said something specific. I guess what I was getting at was the message I was taking away from your post, i.e. you found refractor images to be better.There's no doubt I can see the effect of the CO. But in some cases it comes to light grasp too and that's where the SCT's have the advantage.Actually one question about your previous use experience with the SCT's. Where did you store them? Were you having to deal with any kind of cool down other than relative drops through the night?Clear skies,
Quote:Over perform...I don't know what that entails, ...
Quote:What is the fall off in contrast for an obstructed scope out to about 3 or 4 rings compared to an unobstructed aperture. For moderate obstructions, I think it's about 10%.