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: Organoleptic puzzle
    From: Peter Monta
    Date: 2014 Mar 10, 08:31 -0700
    > Is it possible to cover a star with a wooden match held at arm length?

    Not quite---the match has to be a little larger.  Think of the match as throwing a shadow onto your eye's entrance pupil.  If some of your pupil is not covered by the match's shadow, you will still see the (fainter) star.  Optics people call this "vignetting".

    So the match must be at least 6 mm in diameter to fully block the star's light, assuming your pupils dilate to 6 mm at night.  Alternatively, you could wear some opaque eyeglasses with a pinhole in the center, say of 0.5 mm diameter; then the match will be completely effective.

    I remember reading that the pre-telescope observers had some fancy tricks to increase the angular resolution of their plain sights.  They would arrange for a pin to block nearly all the incoming light, leaving only small slivers at the extreme edges, so that a tiny change in the quadrant's angle would noticeably alter the star's brightness.  Naturally this is most effective with the brighter stars.


    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