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: Loss of accuracy using Sun over Sun with a mercury artificial horizon?
    From: Fred Hebard
    Date: 2016 Jul 18, 21:12 -0400
    The Nautical Almanac conveniently tabulates the SD of the sun on its daily pages.  You can compare those data to your results for index error obtained from touching disks. Those results also allow computation of SD, to refine your technique.

    Fred Hebard



    On Jul 18, 2016, at 5:58 PM, David C <NoReply_DavidC@fer3.com> wrote:

    A very relevant thread for me. I find it difficult to decide when the sun's limbs are just touching.

    A few days ago I took 18 sights. I used my GPS position as my AP. 17 of the intercepts were < 1.5 ', with 13 < 0.5' .   16 of the sights were Away which suggests to me a systematic error.  The IE is 0'. One thought I had was that if the IE was 1' off there would be an even towards/away distribution. However I had carefully checked IE using the two limb method.

    I have concluded that I am not bringing the sun down far enough before  reading the sextant. Next time the sun appears I plan to take another series of sights, this time deliberately nudging  the vernier screw just past the point where the limbs seem to touch.

    Another thing for me to try is sun over sun.  This would give me two limbs to observe, rather than just the one.


       
    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