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    Automatic Plotting of LOP's using graphing calculator
    From: Alex Spradling
    Date: 2020 Feb 13, 22:57 -0000

    Hi everyone,

    First time poster here. 

    I'm writing a navigational program for my Casio graphing calculator. It's going OK. It has a perpetual alamanac for the stars, sun and moon using Meeus's algorithms. It can do St. Hillaire intercepts, time of phenomena etc, and I integrated K.A. Zischka's exact position algorithm for 2 body observations which works fairly well.  

    I'm trying to write a script to automatically plot LOP's using the graphing functions of the calculator, but I'm getting a little stumped.

    I'm trying to program John Karl's Bx method of finding coordinates on the LOP and looping: 

    sin LX = sin d sin HO + cos d cos HO cos BX

    sin LHAX = cos HO sin BX/cos LX

    with Bx =  cosBx = SinL-SinD*sinHc/CosD*CosHc

    this gives Latx and (LHAx - GHA (body)) = point X's Long. along the LOP.

    With each loop I am adding and subtracting .25deg from Bx to produce a list of points along the LOP. Under some circumstances this produces coordinates on the LOP and in others it doesn't. 

    Has anyone attemped this or succesfully plotted LOP's on a graphing calculator? Is there another/easier method? Any assistance woud be appreciated.

    Thank you very much. 

    A. 

       
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