A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Mark Coady
Date: 2016 Oct 5, 11:26 -0700
I was hoping someone might have one of Frank’s wonderful clear statements like “the shadow points south so its negative” on the reason for your reversal of the mathematical sign of DH sun and Dh moon in the equation to get corrected LD.
e.g. Corrected LD = Observed LD + Dh Moon * A + Dh Sun * B + Q We took the moon correction which is positive (parallax trumps refraction) and the sun correction which is negative and reversed the Dh signs from the correction tables entering the equation to get Corrected LD.
My mind keeps trying to say you are going from what you see (sextant reading w/ semi-diameter added)....the human eye observed center to center on the bodies, to what is the actual true distance.... so the corrections don’t change signs... because I want to compare true distance to the bracketed precomputed on either side.....
Obviously my thinking is FUBAR, and I am chastising myself for not seeing “why” .....
IF “Dh moon” is negative in this step, then I assume we also carry the negative into the calculation of Q if it were required?
I’m doing a review of all the different lunar methods I had learned...and I seem to have Amnesia on this one.