NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Lars Bergman
Date: 2023 May 30, 12:47 -0700
Rafael,
I am not familiar with how Freiberger came up with the correction table but it does look like they measured at 10° increments. Nor do I understand how they could determine an error of 1", or 2 or 5 or 7 seconds of arc. If there is a vernier on the drum it might be possible to guestimate down to 3", but probably no better.
I did a least square fit of the given data to the eccentricity formula and found R=303° and E=38". Subtracting the eccentricity contribution from the data points gives the residual errors:
0° 0.0'
10° 0.0'
20° 0.0'
30° -0.1'
40° 0.0'
50° -0.1'
60° 0.0'
70° +0.2'
80° +0.1'
90° 0.0'
100° 0.0'
110° -0.1'
120° 0.0'
Most residuals are 0.0'. The reason for the others are impossible to explain, might be irregularities in the main arc, or in the drum mechanism, or just random measurement inaccuracies. But overall it seems that eccentricity error dominates.
Lars
