NavList:

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.