NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: sextant index error measurement
From: Frank Reed CT
Date: 2006 Nov 9, 03:57 EST
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From: Frank Reed CT
Date: 2006 Nov 9, 03:57 EST
"I checked with a friend who worked in Arizona. He said he had
a
"clear mental image of a range pole at a half mile looking like
a snake through the transit", and that the more important angles
were shot in the morning. But . . . they kept working.
Probably depends on the accuracy you need."
"clear mental image of a range pole at a half mile looking like
a snake through the transit", and that the more important angles
were shot in the morning. But . . . they kept working.
Probably depends on the accuracy you need."
Sure. As I've said previously, the 'normal' terrestrial refraction ranges
from 0.1 to 0.5 (or so) minutes of arc per nautical mile. That's why you can
only trust the dip of the horizon to about that level of accuracy. But for a few
hundred feet, as in the laser test we've been discussing, the terrestrial
refraction is about ten times smaller. And that's just the absolute refraction.
For two beams side-by-side, the differential refraction is smaller again, by an
order of magnitude. In short, it doesn't matter ...under these specific
circumstances.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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