UHC filter or not? Here are two images taken a few days ago. One without filter, the other with OPTOLONG 2" UHC Filter. My Nikon D5500 doesn't see red very well, but for some reason the filter seems to allow most of the light passing through it to be in the red color range. Hydrogen and Oxygen emissions I would guess. Anyway, I seem to like the unfiltered one better! Both taken with 80mm CF apo by Orion, and Celestron Advanced vx mount.