A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Lars Bergman
Date: 2020 Oct 27, 11:24 -0700
I think your excellent result was just a happy coincidence. But - using stars or planets west and east of the Moon and averaging the results do cancel errors in index correction; also if the distances are of similar size centring errors will be more or less cancelled. On the other hand, personal errors like always making the contact too close or too open are not cancelled. To cancel this last type of error you need to use the Sun west and east of the Moon; then the near limb is always used and the average of two watch errors (found from a too large or too small distance) will produce a reasonably mean, assuming the errors are constant of course.