NavList:

"As long as the axis of the scope is parallel to the frame, the centering of the sight line is a matter of preference and viewing convenience. If you raise it up from the frame, you will be looking at the reflected image off the clear glass side more so than the mirrored side of the horizon glass. That's a means of reducing the brightness of the Sun's image.

To verify that the scope is parallel..."

Thanks for confirming that the other axes aren't as critical. As far as frame-parallel, if you get the complete SNO-M set, there are two little 'dioptres", level-sight pieces, to set on both ends of the arc scale with the sextant on its side. This is the 1967 Soviet version of your laser level. These little pieces also help with index mirror verticality. Did other makers provide such a self-sufficient gizmo? I used a clap-board wall 117 feet away to line this up.

Time will tell how good this is when it stops raining in London, but brief sun IE sights are fairly easy, and the two sun discs stick together very well as I wander all over the sky. There's a bit of chromatic abberation on one side of one of the images, but I think I'm at +0.5' IE.

Thanks for clearing up CHO versus SNO. I learned a bit of Russian, but clearly guessed wrong about representing the brand hereabouts ;-)

Cheers,
Richard

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