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: Moon corrections: how computation order affects the result
    From: David Iwancio
    Date: 2020 Sep 3, 14:50 -0700


    When the NA says "the table includes factors X, Y and Z" it's simply saying you don't need to worry about any separate corrections for X, Y and Z.  Bennett pubished a paper in 1985 that mentions correspondence with Yallop of the HMNAO on the construction of the moon correction tables.  The formula Bennett quotes corrects for refraction at the limb, and then subsequently computes parallax at the limb before adding the geocentric SD.


    (Between this and some other papers I've seen, I'm left with the impression that it was Yallop's idea.)

    There's an old joke that there are three ways to do any task:  the right way, the wrong way, and the Navy Way.  The Navy Way is not quite right, not quite wrong, and the reasoning behind it is "Because I said so, sailor!"  A lot of these books and tables are aimed at practitioners of the Navy Way.  The Navy Way can be seen in action in the examples on page 259 in the NA, where the raw sextant reading is used as the entering argument for all tables.  Stepwise corrections to the measured altitude (and trying to interpolate the correction tables) are "refinements" that are "rarely necessary."  Refinements are for landlubber civilians.

    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