NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Accuracy and anomalous dip.
From: Jared Sherman
Date: 2003 Mar 17, 23:20 -0500
From: Jared Sherman
Date: 2003 Mar 17, 23:20 -0500
Arthur- If I understand this correctly then, when the air is warmer than the sea, the observed altitude is too small. And conversely when the sea is warmer, the observed altitude is too large. But one minute per six degrees F seems like it is big enough so that it should have been a "routine" correction in sight reductions, rather than some obscurity to be dug out of an old Bowditch. With a winter ocean near 32F on a cold 5F day...that's an easy 4-5 minute error in the readings! Ditto for those lazy days when the water is near 70F but the air has been pushing the high 90's and local heat from a beach seems to be boiling the air even more. It just seems odd that an error of this magnitude would be routinely ignored.
