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    Re: Sextants and glasses
    From: Paul Werner
    Date: 2014 Mar 27, 07:54 -0700

    Alexandre, You asked:
    “Do you have the Kepler (=day, Sun inverting) scope standard for SNO-T ?”

    Yes, my SNO-T has a Kepler, astronomical, scope too. It can be adjusted to my eyes but I haven't so far made good friends with it. Probably because I am not experienced enough. The main problem is of course the inverted image. But I am going to give it -and me – a serious try.

    You furthermore made it clear that you prefer an astronomical scope. You always use it except in rough conditions.

    I have found support for your point of view in old literature. This is what is written in a book from 1842 (rough translation from Swedish):
    "Good sextants usually have three tubes: one astronomical, one terrestrial and one without glass. The first magnify most and is in every respect best suitable, but for those inexperienced with reversing tubes, observing with a terrestrial tube may be more convenient."

    The astronomical, reversing tube, is also preferred in a book printed 1897. This is what is said in that book about the “inferior” terrestrial tube (also from Swedish):
    "This tube is used by novices performing astronomical observations and moreover when terrestrial angles are measured (if a scope is needed at all) and when in rough sea it is difficult to use the astronomical tube because of its narrow visual field ..."

    Obviously the astronomical telescope was considered the professional navigators choice.

    In modern time – say post WWII – most textbooks on CN take non-inverting scopes – Galilean or others - for granted. The following is from Bowditch, 1958 and 1977:
    "Most modern sextants are provided with only one telescope, but some are equipped with two or more. When only one is provided, it is of the “erect image type,” ... The second telescope, if provided, is of the ”inverting type.”

    Paul Werner

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