NavList:

I think talking about my false telescope might have been a red herring.  I don’t think you even need a sighting tube.  I think you can just look at the horizon mirror.  I tried it today with my Hughes Mates Sextant bringing the top of a tree down to my fence, and it worked OK.  Unfortunately, the sky was obscured, so there wasn’t any sun. With the Sun, the problem would be avoiding looking outside the protection of the shades.  With a sighting tube or star telescope, you can close one eye and press the other against the eyepiece so there’s less chance of an accidental unshaded view of the Sun.  As I recall, the original RAF MkIX bubble sextant had no magnification in the eyepiece.  It was only when they found it safer to fly at night that it acquired a double eyepiece, 1x or 2x magnification in the MkIXBM (M for magnifier).
There’s nothing new about facing in different directions to shoot astro.  When I went through training in 68, the RAF had retained two tail-wheeled Valettas with six astrodomes each along the top of the fuselage so that a course of 12 students could use them as airborne classrooms for the first couple of astro trips.  Apparently, once everyone had worked out their star shots, it was not unknown for the staff instructor to look down the inside of the fuselage and see six pairs of feet pointing in three or four different directions.  Dave