NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Refraction at the horizon.
From: George Huxtable
Date: 2008 Mar 15, 20:47 -0000
From: George Huxtable
Date: 2008 Mar 15, 20:47 -0000
Perhaps, in my previous message, I misunderstood the point Bill was making when he wrote- | I think the refraction between the observer and his horizon *does* | make a bit of difference in how sunsets are timed. Specifically, it | affects how distant that horizon actually is, and therefore affects | the direction of the light-ray that just grazes the ocean surface. | How big is this effect? and I answered- It's zero. By definition, a light-ray that just grazes the ocean surface has only one possible direction; tangential to that surface, and therefore horizontal at that point. ============================= That was not an attempt to be flippant, but now I see what Bill was getting at. And yes, it's true that local refraction will shift that horizon point, towards the observer or away from him. And so the direction of light from out in space, just grazing at that point, will be different also. Bill may well have exposed a flaw in my reasoning. I will need to think about it further, for a while. Watch this space... George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
