Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Exercise #14 Multi-Moon LOP's
    From: Frank Reed
    Date: 2009 May 3, 00:13 -0700

    Brad, you wrote:
    "This is nothing more than good old Saint Hilaire.  We wouldn't try this on a 
    plotting sheet, simply because all the lines are at a relatively shallow 
    angle.  Further, 25 LOPS with 24 advanced LOPS might confuse the living heck 
    out of me, especially when I go for the "cocked hat"."
    Well, at a fundamental level, everything is "good old St. Hilaire". :-) But 
    there's a little more to it than just plotting the "cocked hat". There is no 
    such thing for a dozen sights. Navigators accustomed to plotting a standard 
    LOP fix would be left quite helpless when faced with these sights, and that's 
    probably why this concept is largely unknown. Does that mean there are no 
    On a different matter, you wrote:
    "For similar reasons, the Latitude by Double Altitude methods espoused by 
    Bowditch fell out of favor."
    Actually, it appears that it was never "in" favor in any real sense. While 
    latitude by double altitudes was popular among land-based nautical 
    astronomers and mathematicians, I've never seen any evidence that it was used 
    by practicing navigators (except in classroom exercises). I'm sure it was 
    used occasionally at sea --everything is eventually. But its inclusion in 
    navigation manuals did not reflect "normal" practice.
    And you wrote:
    "This is very evident in the 4th method (variance of declination permitted).  
    That method is twice as long as any other and certainly longer than a lunar."
    There was great competition among the authors of these navigation manuals. 
    Even when one method of working such a problem was more than enough in 
    practice, the publishers could advertise these additional methods and 
    increase their sales. It's important to remember that "epitomes of 
    navigation" were usually private publications back in the 18th and 19th 
    And you concluded:
    "The 'rapid fire fix', at least for me, falls into that category.  Yes, a 
    computer can perform the calculation.  A human, not so much!"
    First, bear in mind that MANY people work their fixes using a computing 
    device, for all sorts of different reasons. There's nothing wrong with it. It 
    may defy the concept of using celestial as a purely non-electronic backup, 
    but there are practical cases where it could indeed be used as a backup, and 
    there are also circumstances (like ocean racing) where there is no reason to 
    avoid electronic solutions. 
    Second, Brad, the fact that you have now come to understand that a "rapid-fire 
    fix" is possible (and not heresy) by seeing it done in software does not 
    imply that software is the only way to go. As I noted in my first post on the 
    topic, getting latitude AND longitude by taking a bunch of sights around noon 
    is no more than one special case of a rapid-fire case. But in the case of 
    lat/lon at noon, there are graphical ways to work the sight which, not only 
    do not require software, but are in fact extremely easy even for beginners to 
    And there remains a question: are there any other special cases of the 
    rapid-fire fix that can be worked by some simple, graphical means? Any ideas?
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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