NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Octant calibration
From: Paul Hirose
Date: 2000 Sep 17, 12:34 AM
From: Paul Hirose
Date: 2000 Sep 17, 12:34 AM
Bill Murdoch, I'm glad my message gave you some ideas. There may be some problems with your plan, though. If your octant has a telescope, it might be difficult to focus at across-the-garage range to carry out your calibration procedure. Also, centering the index arm pivot at the center of your measuring tape circle would be critical, I think. If it's off, you'd get a parallax error. The setup I described for the Mark 3 is not sensitive this way because the "star" is a generated in a collimator. I.e., the rays from the collimator shining on the index mirror are a parallel bundle, so imperfect centering on the rotary table doesn't affect the apparent direction of arrival. Centering only needs to be good enough to assure good illumination as the table rotates to different positions.