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    Re: Calibrating a Bris sextant
    From: Greg Rudzinski
    Date: 2017 Aug 13, 21:48 -0700


    6th Sun upper limb Hc 45° 56.5'  S.D. 15.8' ref. 0.9'  Hs 46° 13.2'

    6th Sun center        Hc 46° 9.8'  ref. 0.9'                     Hs 46° 10.7'

    Average fixed angle for 6th Sun is 46° 12'

    9th Sun upper limb Hc 55° 58.2'  S.D. 15.8' ref. 0.6'  Hs 56° 14.6'

    9th Sun center        Hc 56° 20.5'  ref. 0.5'                   Hs 56°21.0'

    Average fixed angle for 9th Sun is 56° 18'

    note- The calibrated fixed angle for each Sun is used as the Hs for lower limb, upper limb, and center observations. Try to use the same part of the Bris on all observations.

    I hope that you plan to use a sextant (metal) as a standard and alternate observations with sextant and Bris at the beach for a better calibration.

    Greg Rudzinski

    From: Marty Lyons
    Date: 2017 Aug 13, 19:40 -0700

    Right now I am just trying to get the calculations under my belt as I am in Princeton, NJ, 25 miles from the coast and a real horizon . So I use a hand level to sight a ficticious horizon and bring the sun in the Bris down or up to it. Not very accurate but it's helps me get working on the principles which I can refine later at the coast.  I have been using the USNO calculators. 

    Here are a few data points if you don't mind coming up some angles for me. 

    6th "sun"  , 11 Aug 2017,  Upper Limb, UTC 19:49:57   DR for all N 40 22.545', W 74 40.095'

    6th "sun"  , 11 Aug 2017,  Center, UTC 19:48:41         my derived angle 46 10.0'

    9th "sun" , 13 Aug 2017,  Upper Limb,  UTC 15:19:09

    9th"sun",   13 Aug 2017, Center, UTC 15:21:44            my derived angle 55 53.8'

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