Welcome to the NavList Message Boards.

NavList:

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

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    Name or NavList Code:
    Email:
       
    Reply
    Re: Is the focus on the mirror or on the star
    From: Brad Morris
    Date: 2017 May 24, 19:30 -0400


    On May 24, 2017 12:43 PM, "Frank Reed" <NoReply_FrankReed@fer3.com> wrote:


    There is a phenomenon that can influence the apparent focus. Your eye itself has an optical focussing capability. When you are working close to your mirror assembly, your eyes may be adjusting to a nearby focus. When you then look through your sextant, your eyes will not necessarily relax to infinite focus. This may create the impression that you have to focus differently depending how close you are to the mirror. Try this: just before you look into your mirror, look at some distant hills. Allow your eyes to relax to infinite focus. Then look through the sextant scope. The image in the mirror should remain at apparent infinite distance.


    If the AH is contained within the FOV of the sextant, then the observer may be tricked into changing the focus such that the AH is in focus. 

    Infinity focus for the human eye is generally beyond 20-25 feet.  Distant hills, as Frank recommends, will certainly do!

    Brad 

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID Code:

    Custom Index

    Subject:
    Author:
    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