That would be the craters Ptolemaeus, Alphonsus, Arzachel (left, top to bottom, respectively) and for good measure Albategnius on the right (note what appears to be a small crater directly on the summit of Albategnius, measured at approximately 1.5km on an LRO image). The smallest craterlets shown on the floor of Ptolemaeus seem to be somewhat below 0.9km in diameter (based upon measurements done on LRO images), that would be around 0.5 arc seconds.
Taken on the morning of September 12, 2017 using a 9.25" EdgeHD (prime focus) and a ZWO ASI178MM-Cool camera with a Baader Longpass 610nm red filter. Image acquisition in Firecapture, image processing in AutoStakkert! (best 20% of 2000 frames), Registax (wavelet sharpening), with final tweaks in Photoshop CC2017.
This is a crop (1600 x 1200) from a larger frame (3152 x 2086 pixels, near full frame on the ASI178 camera). The seeing conditions were pretty good and the moon was high in the sky, but just as I began my capture session I had low clouds from the ocean and part of this sequence was taken though thin clouds and haze which caused variations in the exposure and detail. If it had remained clear I think I would have had a really spectacular session that would have allowed me to capture more frames and also move to several other areas on the moon. I actually finished by shooting though pretty heavy clouds which compromised my my shots of Mare Imbrium and the southern highlands on the moon (Tycho and Clavius).
Edited by james7ca, 13 September 2017 - 08:23 AM.