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: Precession and Nutation
    From: Mike Freeman
    Date: 2017 Jan 31, 06:37 -0800

    Thank you David & Stan,

    A few things of which I was unaware, am now. The book I am studying (Celestial Navigation for Yachtsmen, Mary Blewitt 1990 edition) suggests when using Polaris or Planet in conjunction with Stars to move each Stars LOP by the amount in AP3270 Vol 1 Table 5. Rather than move Polaris. Possibly 6 of one half a dozen of the other?. It does also suggest the a0 a1 a2 as in Davids second post.

    Initially I became interested in Precession and Nutation because I assumed, possibly incorrectly that the corrections in Polaris tables in NA and the corrections in AP3270 Vol 1 Table 5 were both for precession and nutation, although this is only made clear in Polaris tables. However the reason I became confused is entering argument for Polaris tables is MONTH and entering argument for AP3270 vol 1 Table 5 is YEAR. 

    I also assumed possibly correctly on this occasion Precession & Nutation already taken into account for Sun, Moon & Planets when calculating GHA and Declination from the NA.

    What is not clear is whether any element of P & N is taken into account when calculating GHA Aries. At the moment I am thinking this is why entry arguments for Polaris tables and AP3270 vol1 Table5 differ in respect of MONTH or YEAR.

    Obviously I understand all the information contained in the NA and AP3270 Vol 1 will have changed since my book was published in 1990 but providing the method has not changed I am pretty happy that the application is pretty well explained it is just that I became curious about the MONTH/YEAR anomaly.

    Mike

       
    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