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Re: Accuracy: main shades vs eyepiece shades?
From: Brad Morris
Date: 2019 Jul 27, 15:08 -0400
From: Brad Morris
Date: 2019 Jul 27, 15:08 -0400
thanks Geoffrey.
On Sat, Jul 27, 2019, 3:00 PM Geoffrey Kolbe <NoReply_GeoffreyKolbe@fer3.com> wrote:
Brad Morris said:
"I selected ~ 1900 as a date by which nearly all sextants were made using float glass. Its probably earlier."
"Float glass" - where glass solidifies on the surface of a bath of molten tin, and so is optically flat top and bottom without further polishing - was developed by Pilkington Brothers in the mid 1950s.
Geoffrey Kolbe
