To transform from the above image to this one below a Shadow-filter was used.

What does that do ?
Take an 3x3 array that looks like this

-1    0    1
-2    2    3
-1    0    1

Now calculate for every pixel in the image the sum of the pixels surrounding it using the 3x3 array as a weighing-array. The pixel to the NW gets multiplied with the one to the N with 0 etc. At the end the outcome is divided by the total of the weights (in this case 3). Luckily software exists that allows us to play with images in this fashion.

To transform these images the UNSHARPEN method was used.

This is an old method that is used in ordinary photographic development too.

How does it work ?

First one creates a copy of the original image we will call B.

Image B will now be filtered with a filter that calculates for every pixel the average of the surrounding pixels (including itself). This leads to an unsharp image, hence the name for the technique. So image B is now unsharp and A is the original. We now multiply all the pixels in A with for instance 3 and those in B with 2. Now we subtract the unsharp B from A and we get a sharpened image back. Different grades of sharpening can be used to find the most exceptable value.

And yet another technique was used !

Friend T was so cooperative to send me 12 consequtive images of the same crater. Now I used a technique called STACKING to enhance details. The most important aspect of this is getting all the images aligned as good as possible. So that bright dot to the NW of the crater is in every image at the same pixel. Then several (see the matrix) ways of processing can be used to take advantage of the information. On the top-left a simple mean was calculated for the 12 images, right of that the median was used. Than different degrees of the unsharp mask and finally several filters that were used to deconvolve (nice word :) the image.

What is your favourite ?