This weekend there will be a super moon which I would like to shoot with a 5100. For all critical focusing needs, I use live view because I don't believe autofocus is accurate enough. When viewing the moon in live view, it shows up as only a bright light in the sky with no detail. I focus on the edge of the moon. If, however, I were able to see surface detail, which shows up quite well in the resulting picture, I believe I could get my focus sharper. Is there any way to force the diaphragm to stop down to its preset level while still viewing in live view?