Hi Hy,

I was not aware about this feature, I will try it.
Here is the bible for collimating RC telescopes:
and here is the image on page 14 that would be great to see in viewer in the collimation mode. Of course, the red lines would be difficult to produce and the numbers are redundant.
I think it would be nice to have some kind of a zooming control, where if it is 1, then the preview is as usual, but once you start increasing the value, the corners would be gradually magnified.