A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2020 Oct 29, 06:22 -0700
The Ix azimuth graph uses the same rules as the azimuth formula: sin Z = (cos declination)(sin meridian angle) / (cos calculated altitude). There are issues as to wether to apply Z to the north or south when azimuths are near due east or west. It is helpful to use the prime vertical altitude to decide which pole to use.
The prime vertical formula is: sin altitude prime vertical = sin declination/ sin latitude. The azimuths of prime verticals are always due east or west. Only two place precision is needed for the calculation so it can be done by a pocket slide rule or long hand.