NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Accuracy
From: Bruce Stark
Date: 2003 Mar 17, 11:48 EST
From: Bruce Stark
Date: 2003 Mar 17, 11:48 EST
Fred, Supposing you're bringing the lower limb of the sun to the upper edge of the reflection in the water, a visual phenomenon called "irradiation" could put you north of the truth. Irradiation makes a bright object seem bigger than it really is. When I measure the sun's diameter on and off the arc to check index correction, the average of the measurements is always greater than the true diameter of the sun. Bruce
