From: David Barrie
Date: 2014 Dec 5, 10:26 -0800
I've just looked at the catalogue of sextants in the National Maritime Museum, London ('Sextants at Greenwich' by W.F.J. Mörzer Bruyns, Oxford U. P. 2009). A Ramsden sextant of c.1795 with a vernier to 5" is listed (cat. NAV1106), but most are to 10" or more. Hope that helps.