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: Lunars with Young's formula: always off by several minutes
    From: Lars Bergman
    Date: 2018 Nov 1, 07:16 -0700

    William Porter wrote: "Where am I wrong?"

    I am not sure, but my own calculations are as follows, for 18h46m47s GMT on October 19, 2018:

    GHA Aries        309°53.1'
    SHA Altair            62°  4.7'
    ------------------------------------
    GHA Altair            11°57.8'     This is the "modern" nautical way of doing it, GHA star = GHA Aries + SHA star.

    Working in time, an alternative solution is

    GST                    20h39m32s
    RA Altair             19h51m41s
    ---------------------------------------
    GHA Altair            0h47m51s  

    This result is equal to that above. GHA star = GST - RA star, where Greenwich (apparent) siderial time GST is the time equivalent of GHA Aries.

    I am not sure where Willam got his GST from, is it the value at GMT=0h corrected for acceleration? Anyway, it does not agree with my value. Also the RA is somewhat off.

    My GHA Aries and SHA are from Omar Reis's online almanac, GHA Aries is linearly interpolated between hourly values. GST is just GHA Aries converted to time. RA is calculated from (360 - SHA)/15. This explains why the two results do agree!

    Lars, 59°N 18°E

       
    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