NavList:

GKolbe brought up the narrow field of view. In addition to pre-calcing altitude and azimuth, there is a guide for periscope sextants that has drawings for each of the 57 navigational stars that depicts what they should each look like, that is what are the minor stars around them. That way if you see a major stars but the surrounding image is incorrect you know that you've MIS-identified what you are looking at. 

I don't recall where I learned of this but I saw an example for one of the stars and it immediately made sense.  It might have been several years back when we were discussing the British airliner in Africa that went off course and crashed in the desert when it ran out of fuel.