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    Re: Is the focus on the mirror or on the star
    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
    
    

       
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