The Caves of Copernicus

Copernicus wrote:@Jackie

Unless the resolution is exactly the same in both pairs of images, the features will be of different size.

If the resolution is the same, then there’s the complication that the sun may be shining from the east in one pair, and from the west in the 2nd pair, giving odd lighting.

The main thing you will notice is: a crater is perfectly round in this image pair, and oblong or oval in the 2nd pair. Which shape is correct? The exact shapes never seem to match up between more than one pair of images. You may guess that the round crater is the correct shape, and not the elliptical one, but you don’t really know which one is correct.

Hi!
I might offer something to this. Resolution is weird. If you are taking an image of the lunar surface looking straight down (slew angle=0 ), then each pixel is intercepting the surface based on a solid angle. Thus a surface contained by a pixel which is closer to the spacecraft would have a different resolution than a farther one. This is most obvious in oblique images taken at very high slew angles. There, resolution almost means nothing. Also, the height/altitude of the surface makes a difference. So, no vertical or horizontal resolution means anything except at a gross average level. It is helpful because otherwise we have to do all the geometric calculations ourselves.

The best you can do to get the right shape of an object on the surface is to use images with 0 degree slew angle and adjust the height or width of the image to get both axies the same resolution. For an amount of slew, you need to some fancy Photoshop or 3D model adjustments. Matching all the craters from the baseline image help, but all this is timeconsuming.

Thank you for that explanation, LCG. I realized that the orbiter was in a different position and altitude for each image, which accounted for the differences in the images, but had forgotten about accounting for the differences in altitude for the terrain!

Still, I found that even rescaling the images non-proportionally didn’t work very well for stacking them. It’s too bad, actually, because building high res images of an area such as I did with the Apollo 17 EVA area, is rather neat, though not all that accurate in the end.

Copernicus Crater is quite a bit bigger, and I now have pretty much all of the NAC’s of the interior, so I could theoretically build a high res image of the center of the crater

Anyway, I found one last image of my Candidate “E”. Unfortunately the sunlight is coming from the west, but there is still some interesting detail of the west lip of the crater. Here again is Candidate “E”:



Here is the new image I found of it:



And now at 200%:



Some of the rocks on the west lip can be matched with the first image, but I wasn’t able to completely match them.

C

Hi all!

They released another batch of LRO images. 8 new ones in Copernicus crater. A few updates of the old ones I had found and possibly some new ones.

Happy hunting!

Thanks for the head's up Lunarcaveguy!

As LCG previously mentioned, LROC’s December upload included more new high res images in the crater Copernicus, and I’ve now had time to look through these new images for more shots of the caves and pits previously posted here.

This week, instead of posting in the Odds & Ends thread, I’ll post a new image of pit H4 and also a new one of my “Unknown Object”.

First, here’s a new image of James’ H4 pit:



There was also a second image of this, very similar to this one.

Now… my “Unknown Object”…

This is the first image of it with what I would call normal contrast and lighting.



It is centered in this image, but we need to zoom in to see it better…



As you can see, the object looks quite a bit different here than in previous images. It appears to be a two-tone rock on the edge of a crater or hole. There is a second image available, similar to this, with a bit lower resolution, but it is not as good as this one.

This is probably the best image of it so far, but it would still be nice to have another image of this quality with the light coming from the opposite direction.

That’s it for this week… see you next time!

C

Continuing on with the December updates from LROC…

The December upload contained some higher resolution images taken when the spacecraft orbit was lowered by 20 km for a short time in the summer, but unfortunately there was only one pair of these higher resolution images taken within the confines of Copernicus crater.

I’ve downloaded and searched through maybe a dozen pairs of these higher resolution images now, and the pair in Copernicus is quite noticeably stretched non-proportionally. This is unfortunate since some of the features look a bit different, but there isn’t much that can be done about it.

So here, taken from one of the higher res images, is James’s pit H5:



It is definitely noticeable that the angle is less vertical in this image.

And at 300%...



This is the highest resolution image to date of H5, and the pit floor is even slightly visible. I will point out that H5 appears wider than it should due to the stretching of the image.

Well, that’s all for now… until next time!

C

This week I will present a final update from the Dec15/11 LROC upload, and it is another image of my Cave Candidate D.

This is taken from the same higher resolution image pair as the previous H5 update, and Candidate D looks noticeably different due to the image stretching. It is on the left in this full resolution image:



And now here it is at 300%:



It looks somewhat better with the width rescaled at 75% of the full 300% rescale…



The different angle of the Orbiter really changes the perspective of this cave!

Well, that’s it for now, but the next LROC upload is only just over a month away!

C

Thanks C!!

Just a short note to let everyone know that the next batch of NAC’s has been uploaded by NASA, as of yesterday (a day late). I’ve hardly had a chance to look them over, but am pleasantly surprised to find that there are some very high res NAC’s included this time. Obviously the orbiter is no longer in the same orbit it was prior to August, when they lowered it to take a run of very high res images.

Although there were no new high res images of the caves and anomalies in Copernicus and Aristarchus, there are many other areas left to investigate. And there is always next time, of course… and I predict there will be a lot of low res images of Copernicus!

Enjoy St. Patrick’s Day!

C