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Brad Morris you wrote:  Cmdr Bauer's star to star distances are uncorrected for refraction.  Consequently, they are of little value for the purpose be describes.

Brad
Cdr Bauer’s table, Appendix F in the second edition of his book, is accompanied by a page of explanation where he goes into the effects of refraction and how to minimise it.  Moreover, the table itself is entitled ‘For Practice and Sextant Testing’, not ‘For Sextant Calibration’.  It seems to me that a lot would depend upon the length of the line joining the two stars, its tilt, and how high in the sky it is.  I don’t want to say more until I’ve tried it with a known 'good' sextant.  Currently, I’m stuck with clear skies – too cold to go star gazing, a bit warmer – sky obscured, plus a whole load of light pollution from living near a major airport and having a benevolent Council intent upon leaving street lighting on all night.  I think the result will depend the user’s attitude to celestial.  If like me you’re delighted to get within a couple of miles, and anything less than a mile must be a fluke, then it’ll be OK.  If you consider anything greater than a mile to be failure, then you probably need to look elsewhere.  DaveP