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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Compass correction using sunrise
From: Frank Reed
Date: 2022 Jun 28, 08:21 -0700
From: Frank Reed
Date: 2022 Jun 28, 08:21 -0700
David Pike, you wrote:
"William Bligh is believed to have had amplitude tables with him in Bounty’s Launch"
He may have, but they didn't need them. In the tropics and assuming declinations in the Sun's range, the rising azimuth of a body is very nearly 90°-Dec (where Dec is signed), and the setting azimuth is nearly 270°+Dec. The error from this approximation for Sun azimuth checks (at altitude zero) during the open boat voyage would have been negligible -- about 0.6° at the beginning and 0.3° at the end. For stars, they had Orion setting not long after sunset, and Betelgeuse would have yielded nice azimuth checks every day.
Frank Reed
