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: Ex-meridian sun sights
    From: Greg Rudzinski
    Date: 2014 Oct 5, 10:19 -0700

    Randy,

    See attached excerpts of table 24 and 25 that covers the full range of Sun declination. For today at 34° north a=2.6 . Looking in table 25 under the (a) value of 2.6 the furthest out an ex-meridian can be observed will be 24 minutes 40 seconds from LAN. This means a 49 minute window is available to observe Sun ex-meridians using this table.

    For example if observing the Sun 24 minutes before LAN today from 34° N there will be an ex-meridan value of 25' to add to Ho to then solve as a LAN. Interpolation is required to get this value. It may be easier to use a calculator using the (a) value and the formula (a)(time^2) / 60 =  (2.6)(24)(24) / 60 = 24.96' correction to add to Ho. Or use (.267)(a)(LHA^2) = (.267)(2.6)(6)(6) = 24.99' correction to add to Ho

    Notice that the ex-meridian correction is only 0.7' when 4 minutes from LAN. If precision is only needed to 1' then you will have an 8 minute window to observe LAN without worrying about adding a correction.

    I will try for a real example later today. The down side is that the further you are in time from LAN then the less accurate will be the ex-meridian when compared to a standard LOP reduction for the same observation.

                                                                                                   

    Greg Rudzinski



    File:



    File:



    File:



    File:



       
    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