A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2016 May 25, 10:05 -0700
Zero always looks good but in this case there is quite a bit of slop. Looking at Pub 249 table 6 : Ro' = some value between 50' and 55'. The outside air temperature is a wild guess between 0° and -25° C. This has the f multiplier between 1 and 1.1 which puts the refraction correction between 50' and 60'. Then there is the question of the flight track data accuracy displayed in the passenger cabin.
The navigator also has some play in the rounding process and finally how the pencil is tilted on the LOP plot ;-)