NavList:

Bill,

The way I see this is that Hc is based on an assumed position not the actual position so that the azimuths will differ slightly. Not an issue for the LOP plot. But if an accurate fiber optic gyro were to be checked to it's precision then I would use Ho (not Hc or Hs)to calculate azimuth to the tenth of a degree.

Greg Rudzinski

Using sun compass for calibrating boat compass
From: Bill B
Date: 2014 May 7, 10:34 -0700
When reducing a sight one would traditionally compute the Hc, then the azimuth from the Hc (although the azimuth can be computed directly without the Hc).

This is fine for plotting an LOP, but it raised a concern for me. Is the azimuth I obtain for the celestial object tied to its Hc, rather than its observed position with refraction?

Perhaps the accuracy of a shadow sun compass (as opposed to a William Burt solar compass )on a light to medium displacement sail craft is such that it is a moot point?
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