A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2015 May 10, 23:25 -0400
Of course, Fred, that method works too, albeit with some arithmetic involved.
I've found that the superimposition method works just fine for me, allowing me to simultaneously adjust my index error and my side error to zero. Set the index arm vernier to zero. Adjust until the images are superimposed. Viola, zero index error. No math. No arithmetic. No fussing over on or off the arc.
Isn’t the usual method is to touch one image to another, measuring the semi-diameter?
On May 10, 2015, at 10:11 PM, Brad Morris <NoReply_Morris@fer3.com> wrote:
Superimposing the sun's image onto itself or the moon's image onto itself is a highly effective method of determining the index error.
Just watch that you don't blind yourself by observing the sun without shades! That pain you feel in your eye is a warning! (Slight humor should be noticed here!)
BradOn May 10, 2015 5:07 PM, "Herman Dekker" <NoReply_Dekker@fer3.com> wrote:
Thanks for the info.
There is no free sight around possible in the backyard. It is dark now, so I used Venus, that works. The index error is now back from 55' to zero, as long as it stays with a plastic sextant. Is a high cloud with a sharp edge usable for index error? This is just an idea, as nothing else is possible?
Frank can you explain: What is the Sun test on the Moon?