NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: As The World Turns
From: Geoffrey Kolbe
Date: 2013 Feb 22, 18:27 +0000
From: Geoffrey Kolbe
Date: 2013 Feb 22, 18:27 +0000
Norm Goldblatt wrote:
It is actually quite a complicated problem. Edge diffraction means that geometric angle alone does not define the distance at which you start seeing the star, or Jupiter, again. And then there is limit of brightness below which you will not see the star at all - but you will still see Jupiter. And that all depends on how dark the rest of the sky is. There are some interesting papers on this subject.
Geoffrey Kolbe
Sometimes the simple things are the most provoking. Sitting comfortably in my hot tub tonight, head cradled and stabilized in a cozy corner, I watched Aldebaran become occulted and then emerge from behind a distant telephone wire. Tomorrow, I'll try for Jupiter. I wonder if the angular subtense of the wire is less than that of Jupiter's disk. It well might, as these days, Jupiter subtends 40 sec. A 1/2 inch cable subtends the same angle at a mere 219 feet.
It is actually quite a complicated problem. Edge diffraction means that geometric angle alone does not define the distance at which you start seeing the star, or Jupiter, again. And then there is limit of brightness below which you will not see the star at all - but you will still see Jupiter. And that all depends on how dark the rest of the sky is. There are some interesting papers on this subject.
Geoffrey Kolbe
