NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Minus index corr better than plus
From: Paul Hirose
Date: 2000 Jul 26, 05:01 EDT
From: Paul Hirose
Date: 2000 Jul 26, 05:01 EDT
One reason I prefer a negative index correction is the same one some of you stated: it's easiest to read index error when it's on the arc. But I will say that reading a few minutes off the arc is not hard. Just visualize the 59' mark on the drum as -1', 58' as -2', etc. Fractional minutes can be estimated by eye, or you can visualize the vernier numbered in reverse as well. The other reason I like a negative IC is that it's the same sign as the dip correction, so there's less chance of a blunder. At least that's the case with star shots, since the refraction correction will also be negative. Shooting the Sun's upper limb will give all negative corrections too. With the Moon you're going to have both + and - corrections regardless of index correction sign, unless the shot is quite high-angle.
