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: Time Sight Problem: Joshua Slocum Lunar
    From: David Fleming
    Date: 2011 Mar 25, 16:22 -0700

    Now that I have asked the question I believe I can answer it.

    For the afternoon sun sight, we have
    hs = 38d 39m
    -3.9m ic and 4 ft ht of eye
    +14.8 main ( ref & semidiameter)
    ho = 38d 49.9m = 38.83166...

    and NA gives Sun GHA(t) = (t-21)14.963 + 134.79
    ( ie this equation gives values of sun GHA around time of interest )

    with DR Lat of 11d 4m S and above ho

    by solving Law of Cosines for LHA we find LHA = 38d 38.62m = 38.64366...

    thus if DR Lo were = (t-21)14.963 +134.79 -38.64366.. then we would have our sun sight anytime throughout that period.


    Now we need a similar equation for the lunar observation. Getting a similar equation for DR Lo (t) which would give the lunar observation. This could be a little harder due to variation of lunar dec but it is probably sufficient to ignore that and get a linear expression.

    Equate the two expressions and the value for t is GMT for the pair of observations.

    Dave Fleming
    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    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