Using the recommended magic marker, I coated the edges with black ink. The ink wicked into the cracks and make them quite visible, even though most are hard to see without some sort of aid. You can see the shear plane on the lens at the left in Fig 8, and also several starting ying- yang cracks. This is a 200 second exposure taken through the I filter. Alpha Serpens Caput at RA 15h 44m and Decl.
North is to the top, and west is to the right.
The raw image was 2k x 2k at 16 bit resolution. It has been binned 2 to 1 in x and y, and then put into .gif format to conserve space. Many of the stars are saturated in this image. That is OK for us. We are interested in the stars that are not saturated, which is most of them.