A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2019 May 1, 15:45 -0700
Be sure the optic is perfectly focused and the measured limb and horizon are in the center of the optic. Use enough filtering on both the Sun and the horizon. Correct for temperature and pressure. Double check height of eye and perpendicularity of sextant. Try doing some lunars using Frank's online calculator to compare to natural horizon observations. Also try using an artificial horizon to compare to the natural horizon observations. Even if everything is done correctly there may still be some remaining systematic error. This is best handled by observing three bodies with azimuths differing by 120° or four bodies with azimuths differing by 90°.