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
    Index Error - Comparison to SD per Nautical Almanac
    From: Jim Rives
    Date: 2020 Nov 23, 06:01 -0800

    I have been doing lunars pretty regularly since the beginning of the year.  Normally I take the opportunity to determine my Index Error using the Sun-on-Sun method, as it seems to be more reliable than the split horizon method.  I had expected to be able to confirm my calculation of IE by comparing the resulting calculated Semi-diameter (SD) with the SD published in the Nautical Almanac.  However, I noticed right away that it was off... so initially I thought it was some sort of rounding error.  However, the data for the past six sights shows a calculated SD that is consistently .2 minutes smaller than the published SD.  The IE determined averages +2.6 pretty consistently.   I had thought that I should be able to come to the published SD normally.  Can anyone make any suggestions as to what could be causing this.  Should I be able to agree to the SD per the Nautical Almanac?  


    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