NavList:

As some of you may recall, I asked about mutliple extra suns in my view doing a solar index correction check.  Careful checking unearthed the culprit. the two oval head countersunk screws that attach the scope mount to the frame (should be self centering) were just loose enough to permit the scope to swing upward slightly. This sextant traveled many a mile over road shipping to get to me so thats no surprise, and an easy fix.

But looking at the fundamental geometry of the C & P, caused me to pull out my ASTRA to find the same puzzling design.

The index mirror filters, when swung into view onto their stops, on both sextants swing into the path of the upper portion of the scope objective lens. It even appears to be significant encroachment. I stuck the plain sight tube (smaller diameter) on the astra and you can still see the bottom of the index filters through the sight tube.

It caught me by surprise.....the reason I would assume is that it keeps things compact..at the same time it suggests we are only working with the center area of the incoming objective....other than for light gathering......Is this the case?  

In other words..why doesn't the encroachment munge things up?