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: Wharton & Field's Hydrographical Surveying
    From: Fred Hebard
    Date: 2004 May 9, 23:34 -0400

    On May 9, 2004, at 4:52 PM, Robert Eno wrote:
    > Fred Hebard wrote (a quote from Wharton & Field's):
    >> For these observations in an artificial horizon, Wharton recommends an
    >> eypiece shade rather than the swing-out sextant shades.  He also
    >> recommends multiple eyepiece shades of varying optical density.  He
    >> discusses examination of errors caused by swing-out sextant shades.
    > Robert responds,
    > I don't know if I buy the bit about swing out sextant shades
    > introducing
    > errors. Perhaps this was true back when that book was written, however
    > can
    > the same be true for modern sextant shades?
    and Fred:
    You bet.
    I heard of an example not too long ago of a modern, "quality"
    manufacturer who shipped un-parallel shades.
    The eyepiece shade avoids any swinging shade effects, including ones
    that aren't there :)
    At appropriate altitudes, swinging shades also will reflect a pretty
    strong image of the sun right into the field of view.

    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