NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Is the focus on the mirror or on the star
From: Luc Van den Borre
Date: 2017 May 25, 13:46 +0200
From: Luc Van den Borre
Date: 2017 May 25, 13:46 +0200
On 24/05/2017 08:33, Randall Morrow wrote: > I am puzzled. I have been told that when I look at a reflected star > image I am focussing on a body at infinite distance. That makes sense > intuitively and with optics of things seen in mirrors on earth. But, if > that is the case with a star, why do I have to adjust focus as I move > toward or away from the mirror to take sights. There is no doubt about > this. It is an indisputable fact. I have seen this in thousands of > sights. If my focus is on the star at infinity I should not have to > change my focus. Please explain this. My suspicion is, that since vision > happens in the brain and not the eye, that my focus is the surface of > the mirror a few feet away and not the star at infinity. Please comment. Are you using a second-surface mirror? I think that would result in some chromatic aberration, which would become more noticeable further away from the mirror. Luc
