NavList:

Dear Alex,

I remember seeing some soviet manual with star/star sextant check recomendations, but can't find at the moment among my files. If I remember corectly, the idea was to measure angles from Polaris to other navigational stars. In practise I don't think the method was widely used, maybe only by some navigation enthusiasts (this is only my speculation). 

Today (thanks God! :)  ) we can calculate star/star distances very accurately and definitely are not limited by altitudes or particular stars. Even non navigational stars can be used.

Returning to the topic of sextant accuracy: have you experimented also with other sextants, not only SNO-T? If YES, what was your experience? Have you tried vernier sextant? I am curious what was the real accuracy of the instruments of this kind. One possible advantage of vernier sextants could be the lack of micrometer mechanism with its movable parts that causes additional errors. But I have no experience with the instruments of this sort. 

Modris