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
    Two plots, same LOP
    From: Peter Hakel
    Date: 2011 Oct 29, 11:18 -0700
    This July 2011 posting from Michael Bradley prompted me to finally extend my intercept.xls spreadsheet to include additional LOP properties that allow its plotting in alternative ways.  The following video:


    shows one of those options in its second half after the more conventional intercept-azimuth plot.  Since the video focuses on the output (cyan-colored) part of that spreadsheet, I attach a screenshot of the whole thing. 

    I also acknowledge Frank R. and Henry H.'s contributions to that "time sights" thread.


    Peter Hakel

    From: Michael Bradley <mcbradley_uk@yahoo.com>
    To: NavList@fer3.com
    Sent: Monday, July 18, 2011 2:50 PM
    Subject: [NavList] Re: When did "time sights" fade away?

    Thanks Henry - beautifully put.
    With me the concept has certainly not faded away, I invariably use it in the form of 'Longitude By Chronometer' with an Azimuth. Such a sight reduction produces an LOP more easily plotted than any intercept solution because the navigator can choose a Latitude, mark off on it a single computed Longitude, and draw the LOP through the tick mark using the computed Azimuth to align the plotter. Less marks on the chart/plotting sheet, just one line to draw, and much easier to do bouncing about on a 32 ft yacht.
    Aside, I use the complementary method of my solution for what might be called an 'Ex Meridian Latitude' with an Azimuth, having chosen an easy Longitude for the single tick mark required for plotting the LOP.
    Needless to say I've got it all running on low power IT hardware with my own software, so the sight reduction and plotting is a piece of cake to do on the yacht for any sight.
    When I enquired about commercial software that could produce a Longitude by Chronometer and Azimuth sight reduction from of a well known broadline US Celnav specialist, there was none to be had. I did get from the other end of the phone an audible intake of breath of the type normally used in responding to mad people.
    One senior member of the list has seen and used the software. He couldn't get out his rut that Long By Chron was intrinsically inaccurate, a notion that you have elegantly demolished: thankyou again Henry, the person concerned wouldn't or couldn't take the refutation from me.
    I showed the software to a local Celnav instructor with his own practical sailing school - his response was that he 'quite liked to see a spider's web of lines on the chart'.
    Having chipped in to the list once before to mention the ease of plotting arising from the Long By Chron and Azimuth method without a single response from the rest of the list, I'm happy to leave them to their 'not made here' prejudiced inflexibility. If it makes them feel better to plot more lines than I do - bless 'em all.
    Must stop - sailing south tomorrow morning.
    55 North
    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


    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