NavList:

Thanks, I do understand the notion moving one degreee away from the GP and your Ho decreases by one degree and the ZD increases by one degree.  But let's say you are at the Tropic of Cancer  on the summer solstice (same declination for the sun as your latitude) and assume your longitude is zero degrees (I have no idea where this is--just an example). It you look at the sun at sunrise or sunset, where is the GP of the sun. I assume it has to be 90 degrees and 5400nm away?  Thanks