Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    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.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site