Like a bunch of other people, I was recently motivated to purchase an AR style weapon. I went exploring to see what type of night vision scopes were available. I noticed that there were night vision scopes that were made to be placed, in-line, with other scopes which had a reticle and maybe magnification. Most of the stuff I saw had this with a leapold, aimpoint, or trijicon. Some of the scopes were connected to the night vision scope. Some were not; there was space between the two. I looked around and did not find a discussion of this. For the case were they connect (or touch) is there a standard connection? Is there more than one connection type? How do I know what scope to pair with a given night vision scope? How well does the "in-line" thing actually work?