A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Frank Reed
Date: 2018 May 13, 19:21 -0700
Ed, you wrote:
"pre-cleared Lunar ends up 117°49'16" after both semi-diameters. Can't account for the 1' subtraction, certainly not augmentation which would have been additive."
Considering its position in the sequence of corrections, I presume that the 1' is nothing more than the instrument error or what we call today "index correction". In other early sights, this is simply labeled "Corr" for correction. I wonder when the modern term became common...