A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Iwancio
Date: 2022 Jun 5, 22:08 -0700
I put together some code to find least-squares approximations for a few formulae using the NA refraction tables as the inputs. Refraction is in arcminutes and altitudes in degrees.
r = 0.92 * cot(h + r * 2.86)
- Errors for (fomula - table) range from 0.5' to -1.0'
- The model says this should be the same thing as r = cot(h+ r * 2.63)
- If 2.86 * r is small and r2 is approximately 0, this all reduces to r = 0.92 * cot(h)
- The 0.92's start to differ with the third decimal place.
h = 81 / (h + 2.3) -1.1'
- Errors for (formula - table) range from 0.9' to -0.4'
- If you want to use this as a "first guess" in the Bradley model, r = cot[ h + 3.6/(h+2.3) - 0.05]
- You can probably drop the 0.05 at the end.