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    Re: Asymmetry in i.c.
    From: Tony Oz
    Date: 2019 Jun 8, 02:34 -0700

    Dear Igor,

    I'd rather measured Sun's SD across its' horizontal direction - to eliminate the refractions effects the best possible way.

    As Brad has already suggested - I always turn the drum in the "increase" direction (to eliminate the backslash).

    And my favourite formula for I.E. determination is:

    360° - (360°xx' + 359°yy') / 2

    where the xx is the minutes value read directly off the drum for the "on-scale" index position; the yy is the "off-scale" minutes value. This works if the initial I.E. is less than 1°.

    The resulting value has algebraic sign and should - as such - be always added to the sextant reading.

    Warm regards,
    Tony

    60°N 30°E

    PS

    Did you study the "Фатьянов А.И. Практическое руководство по выверке и определению поправок штурманских приборов на судах (1976)" book as well?

    In the similay way I can obtain the SD:

    (360°xx' - 359°yy') / 4

       
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