A bit of a different perspective on some craters

[Asellus]

I was imaging the moon a couple of weeks back, looking at Clavius and having a read of Wikipeadia. They have a Lunar Reconnaissance Orbiter image from directly above. I was wondering if I could some how warp my image to get something similar. Thinking about it I realised that if you take the latitude (north/south) and tilt the image left-right by the same angle you'll locally remove that destortion. You can do the same with longitude (east/west) by an up-down tilt of the same angle giving an approximate view from directly above, but with a smaller image (see below). This works OK at the exact latitude/longitude but destorts the rest of the moon the further you are away from that point (like it's in a hall of mirrors at the fair ground). Results for Clavius (58.4°S 14.4°W) were OK. The image below shows a blow up of the original image, the tilted image, and an image generated from the NASA LRO data https://quickmap.lroc.asu.edu/ .

My method was align my original image North-South (did this by comparing a couple of features from the NASA SVS daily image ( https://svs.gsfc.nasa.gov/4955 ) - you can actually use these images to have a play with tilting in the image software of your choice if you don't have a handy image of your own. Then used the 3D Transform tool in GIMP to tilt the image 58.4 degrees left-right and 14.4 degrees top-bottom. There are two options here either +58.4 or -58.4, both work but once chosen only one of + or - 14.4 works. They produce very similar results, but one of +/- 58.4 looked slightly better to me. You also need to correct for libration, but I found as my original north-south alignment was never totally acurate once I'd dialed in the latitude/longitude it was best to pick a small craterlet somewhere near the centre of the region of interest and just tweak the left-right/up-down tilts a little by hand to make it circular.

Results at the bottom 🙂

Obviously once this worked I had a play at how close to the limb you can get (the answer is very!). I've got some more examples if people are interested.

Edited February 20, 2022 by Asellus
typos

[DrMike]

That’s amazing, and something I will try, once the weather improves. Well done and thanks for sharing.