Scopes: 10" dob, 13" dob, 4" refractor
"Only gold is money, and nothing else. " - John Pierpont Morgan
I ache, therefore I am
Criterion RV-6 (1977)
Astro-Tech AT-10D (2011)
I don't buy scopes often
Quote:With sufficient optical power the main craterlets can be seen under full moon illumination as light spots.
C10NGT, Z8, 150 Rumak, XLT 150, C6, C5, SW5 Newt, 4.5 Ball, C102GT, C90, ST80, A70LF; 15x70, 25x100; Burgess BV; Paracorr II; T6 2.5, XO 2.58/5.1, Ethos-SX 3.7, Delos 4.5, TV Plossl 7.4-26, BCO 10, Hutech HC 12.5, Sterling 12.5-25, ES100 14, CZJ H 16/25, CZJ O 16, M5k UWA 24, T5 31, Ultrascopic 35, Titan-II 40; Bino Pairs M5k UWA 6.7, Baader Zoom 8-24, M5k SWA 24, TV Plossl 26, RKE 28.7; Zooms NZ 2-4, NZ 3-6, Leica ASPH 8.9-17.8, Baader 8-24; Baader Zoom Barlow, VIP Barlow
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
Quote:Quote:With sufficient optical power the main craterlets can be seen under full moon illumination as light spots. Yes, this is true. But sticklers will say that you're not really "seeing" the craterlets, you're only detecting their albedo spots. Personally, I'm not that persnickity.Mike
Quote:With the "white dot" albedo features, you are at the very least, "detecting" some of the craterlets. However, when the moon is not full, it takes a little more aperture (and good seeing) to resolve the craterlets and show them as the true pits they are than it does the tiny white spots that some of them generate under full moon illumination. Clear skies to you.
Quote:Nirv, here's an excellent guide to Plato's craters. I've managed the big 5 A through E. A through D one one night long ago and picked up E recently. Add a few others as specks, I think my own total is about 11, if memory serves on the speck count.Good luck, it's a great challenge. The times above are nice for picking them up, maybe catch the waning moon in that seeing might be a tad better later in the night.
Quote:Initially, if crater diameters are (understandably) off by +/- 0.2 miles, that changes which ones can be resolved a bit. But, I did nail E one in 150mm, nothing smaller on Plato, yet. So, at least that one is doable and above the resolution limit for that aperture as a minimum.
Quote:I am not sure what is meant by optimizing for high resolution lunar and planetary imaging.
Quote:Any spot of the lunar surface, like the rim of a craterlet, can act as a point source of light that my optic/eye can detect even though my optic isn't capable of resolving that feature.
Quote:Those multiple points would have to be separable by my optic of course otherwise they'd appear as one spot.
Quote:Dawes, or actually Lambda/D as an approximation of Dawes, is about 113.4/Dmm. It changes a little with the magnitude of the point source, but we can assume the moon to be mostly bright (crater rims) and any diffraction affects having relatively stable and modest magnitude.
Quote:...often with no discernible rim...as a result contrast on these very small features is softened still.
You need an isolated point of brilliance - again - against the backdrop of the shadowed terminator/night side.
Quote:But what about specks at higher sun angles? Do we see fewer or more of them? Does the crater need to be much larger at those sun angles? And does Plato's dark floor help bring them out?
Quote:We've seen elongated specks over the terminator, sometimes I even focus on and evaluate seeing with them. Thinking about it, though, at those sun angles those features are most likely higher peaks. Yea?
Quote:Mike, we might see more albedo features at higher sun angles. That seems intuitive and might agree with my own experience. Or at least my own perception. But what would be the mechanism that makes a crater look like a bright spot instead of disappearing into the high sun lit surface?
Quote:I probably do more double star work that small lunar crater spotting. Maybe because doubles are easier. What I mean is, we can split a Raleigh double fairly easily and quite readily almost regardless of the seeing. But to resolve a crater at that same level of resolution requires an exceptional night. When I first got my scope, I was hunting the smallest craters I could possibly see. It took some effort and very steady moments. A Raleigh double is not nearly as taxing, nor is a Dawes split for that matter. Surely that's a difference in object type and contrast involved.