# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Using sun compass for calibrating boat compass
From: Sean C
Date: 2014 May 7, 15:40 -0700

Bill,

When calculating the azimuth using the NA formula (in which Hc is a factor in determining azimuth), it appears the effect that the Hc has on the azimuth increases with the altitude. However, this effect remains small until the altitude gets close to 90°.

Here's a totally random example:

LHA: 320°
Dec: N25°
Lat: N30°

Hc: 54° 20.8'
Zn: 88.2°

Now, if I calculate the azimuth using an Hc of just 20° I get 88.8°. Using an Hc of 60° I get 87.8°, and with an Hc of 80° I get 83.8°. So, for this example, an error of at least +/- six whole degrees would not effectively change the azimuth.

Regards,
Sean C.
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