NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Dip uncertainty
From: Alexandre Eremenko
Date: 2004 Dec 6, 18:23 -0500
From: Alexandre Eremenko
Date: 2004 Dec 6, 18:23 -0500
On Mon, 6 Dec 2004, Bruce Stark wrote: > Climb on the buoy and look at the horizon through the > prism. The angle between the horizon and where you see > it through the prism will > be huge. > Now go twenty miles away, and from a height where you can > see both the prism > and the true horizon, look (you'll need a powerful telescope) > at the prism. > The horizon you see through the > prism will be only slightly out of line with > the true horizon. IF you are able to see the horizon from 20 miles THROUGH the prism, the correction to the normal dip in these two experiments will be the SAME, namely, the angle by which the ray is turned by the prism. Its another matter that from 20 miles, no matter how powerful your scope is (and assuming ideally transparent atmosphere, better no atmosphere at all) you will not be able to see the horizon THROUGH your prism. What you will see is some spot of the sea surface near the prism. Just draw a picture, assuming that the angle of deflection of the ray by the prism is the same in both experiments. Alex.