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
    Name or NavList Code:
    Email:
       
    Reply
    LHA and Meridian Angles
    From: Bob Goethe
    Date: 2015 Apr 2, 13:02 -0700

    What is the rationale behind the use of LHA in sight reduction rather than the meridian angle, per se?  I am presuming there is either a logical or historical rationale, but can't imagine what it would be.

    If you are taking a sextant sight and the GP is on a meridian 45° east of you, then the meridian angle is 45°E.  It seems like it is merely adding another step to turn this into LHA 315°.  I know this step only takes another 3 or 4 seconds to perform.  I can't understand just why the navigational world considers this worthwhile.

    If one uses MA without converting to LHA, then in Pub. 249, he invariably uses the LHA angles along the left margin.  But clearly, Pub. 249 is designed on the assumption that its users will be using LHA and not the meridian angle, per se.  Everyone will be using right-hand column for morning sights of the sun, and the left hand column for afternoon sights.

    --------------------------------------
    As an aside, the meridian angle seems to show up in diagrams labelled at "t".  Is the use of "t" one of those arbitrary historical choices that mathematicians made, or did Marc St. Hilaire use it as a snappy acronym of some French word?

    Thanks,

    Bob

     

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

    Enter the email address associated with your NavList messages. Your NavList code will be emailed to you immediately.
    Email:

    Email Settings

    NavList ID 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