Last year I’ve acquired an image of the well known crater Posidonius under excellent seeing conditions. At that moment I was mostly interested in processing the shot as a “nice-looking” lunar image. Going back to that data, I’ve now reprocessed the image without significant post processing (like shadow enhancement, crater halos elimination or strong sharpening). I’ve done this in order to reveal the smallest details present in the image. These details are in the range of 500-550 meters, with a bit better resolution on the small rimae inside Posidonius.
The technical data: 355mm F/5 Newtonian at F/~30 using a Baader Hyperion 2.25x Barlow and extension, ASI 120MM-S camera with a Baader Red filter. Seeing was close to perfect (9/10), but transparency a bit lower at 4/5 due to some dew on the secondary mirror, thus resulting in slightly diffuse halos around the bright crater rims.
The image shows quite well the famous sinuous rille on the floor of Posidonius (compare with the LROC image at the bottom of the post).
First, the reprocessed image:
And the old version, with a lot of post-processing:
Also a measurements result, applied onto the old version:
What a superb crater Posidonius is, both in images and at the eyepiece under good seeing conditions.