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
    or...
       
    Reply
    Re: Finding IC for A-12 bubble sextants
    From: Frank Reed
    Date: 2021 Oct 6, 07:01 -0700

    Ed Popko, to David Pike (expert bubble sextant user!), you wrote:
    "Thanks for the advice. I think I have to back out Franks corrections for standard pressure etc.  But yes, that's a simple way to start."

    It's a simple way to start and end. Really there's nothing more to it. And no, you don't need to "back out" any of the corrections. That's just odd! The app shows you what your sextant should read. Set it for the right object (probably Sun, Center) and the proper horizon type (bubble), and you're all set. Any difference between what you observe and what you see in the app tells you that your GPS is wrong (not likely... GPS does occur in the continental US where we're located but it's highly localized) or it tells you that you or your sextant are wrong. And "wrong" here is just "index error". Of course it might be a more exotic "arc error" that varies with the measured altitude, but that's not likely to be detectable within the usual rather low accuracy limits of bubble sextants. The error you see is your index error. Of course you should make sure the instrument is stable with the bubble centered, and you should average over a series of trials. Other than that it couldn't be easier.

    Link for those unfamiliar: ReedNavigation.com/GPSantiSpoof/

    Frank Reed

    File:


       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    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:

    Email Settings

    Posting 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