NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2010 Mar 24, 08:45 -0400
Hi Scott
There may be some degree of prismatic error, depending upon the angles that you are viewing objects thru your glass. As light passes thru regions of differing indices of refraction, the light
will be refracted towards or away from a normal to the interface as a function of Snell’s Law. The same prismatic error can occur in your sextant’s shades, should they not be perpendicular to the optical path. Think of your glass doors as yet one more “shade”,
which must be considered in the optical path.
Another issue you may have is the Dip Short. If the distant lakeshore is visible, then you do NOT have a horizon, you have a dip short horizon. There are ways to deal with this, you are not
alone with this issue. Bowditch, and others like Norie, will provide the appropriate correction.
Best Regards
Brad
From: navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com]
On Behalf Of Scott O'Connor
Sent: Tuesday, March 23, 2010 8:04 PM
To: NavList@fer3.com
Subject: [NavList] shooting indoors
Maybe a dumb question. I live where it is very cold much of the year, but can get sextant shots through a sliding glass door to a distant lakeshore as horizon. Does shooting through the glass affect accuracy of the sights, from a scientific basis? Thanks
for the input.
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