A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2017 Jan 18, 04:59 -0800
On a DIY sextant or plastic sextant there will be arc errors measured in full minutes through the arc. Production metal sextants will have just tenths of a minute arc error through the arc. The fastest way to generate an arc error table is by using a metal sextant as the standard as Frank has described. I was able to check arc error on Ebbco's and Davis plastic sextants through 120° of arc in less than an hour. Then to verify the table use artificial horizon, lunar, horizontal angles, and star to star observations. I now own four plastic sextants and have arc error tables for each. 0 to 25° seems to have small errors (0 to 2') with max errors ( 5' to 8') above 45°. There must be a reason for this ? Once the table is verified then tape it to the sextant for future use. A big improvement in accuracy should follow.
From: David Pike
Date: 2017 Jan 17, 06:07 -0800