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    Re: The Length of a Day
    From: Ron Jones
    Date: 2016 May 26, 16:45 -0700

    The attached PDF shows the altitude of the Sun as viewed from Ediz Hook (48° 8.5' N 123°  26' W) on May 27 2006.  I use graphs like this which illustrates the length of day light & twilight as viewed from a specified position and date to illustrate to my students how these times varry through the year from a specified position. This graph was produced by my Excel Celestial Navigator Workbook that I use in teaching my USPS JN & N classes. The Celestial Navigator workbook version 12.5 cam be downloaded from:



    The Celestial Navigator Workbook contains the following worksheets:


      Nav Bodies .. GHA, Dec & other data for Sun, Moon, Planets & Stars for a given date, time & position

      Sight Planning .. Help in selecting sights for a two or three body fix

      Sight Averaging .. Shows a graph of up to 10 sights and allows bad sights to be removed

       Sight Reduction .. Using Law of Cosines Method +NASR +Time Diagram +Meridian Diagram

      SR 96 .. Sight Checker for USPS Form SR96

       SR by DC .. Sight Reduction by Direct Computation, Nautical Almanac pages 277--> 285

      Hs to Ho .. Calculating Ho from Hs, Nautical Almanac pages 280 & 281

       Moon Ha to Ho .. Nautical Almanac Moon Altitude Corrections

       Meridian Transit .. Latitude by Sight on a body at meridian transit

      Polaris .. Latitude by Sight on Polaris, Nautical Almanac pages 274 & 275

      24 Hc & Zn .. A graph of the Sun's Altitude and Azimuth vs Zone Time for a given date & position

       Analemma .. A graph of the Sun's Declination vs the Equation-of-Time for an entire year

      NAV Coordinates .. Celestial Navigation Coordinates & the Celestial Sphere

      Yellow Pages .. Nautical Almanac Increments & Corrections

       DR 2 Body Fix ..Two Body Fix,  from a DR position

      AP 2 Body Fix .. Two Body Fix, from an assumed position

      DR 3 Body Fix .. Three Body Fix, from a DR position

      AP 3 Body Fix .. Three Body Fix, from an assumed position

      Set & Drift .. Calculates set & drift +Track & SMG + Course to Steer & SOA

       60 D ST .. Speed, Time & Distance calculations

       Interpolation & Data Conversions

      Arrival Coordinates .. Calculated using mid-latitude sailing equations

      Course & Distance .. Calculated using rhumb line equations

       Great Circle Route .. Calculates Great Circle Distance and initial course heading

      Rhumb Line .. Distance vs. Great Circle Distance

      Tides .. Rule of 1/12 for Tide Prediction





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