Section III: Latitude and Longitude

Section III of the Sight Reduction Form is used to find the Local Hour Angle (LHA) and Declination of a celestial body. These are the two angles which define the position of a celestial body on the celestial sphere. Together with Assumed Latitude, these will be used to find the values needed to plot a Line of Position.

  • We’ll look at Greenwich Hour Angle (GHA) in our first video.
  • Our second video explains how to calculate the Local Hour Angle (LHA). This value will be used in the Sight Reduction Tables.
  • Our third video, Declination, covers this calculation which determines the celestial body’s position relative to the celestial equator.
  • Our final video for Section III, Assumed Latitude, will walk through how to use Declination to determine whether we use “Same” or “Contrary” in the Sight Reduction Tables.