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: Scrap paper with time sights c.1870
    From: Frank Reed
    Date: 2013 Apr 4, 08:20 -0700

    Lars, you wrote:
    "Second, I missed all observations on the "blue-4". Thus, the October voyage started at 31N 72W on October 22nd, but continued until October 31st, after passing through the Bahamas, south of Florida and ending off the Mississippi delta. In all this gives 41 time-sight reductions."

    Oh that's great. I had looked over the pages after you posted your previous summary, and I was wondering if I had missed something.

    "In the October voyage, the chronometer is gaining. Between 26 and 28 October there is a large jump in the correction, presumably based on a terrestrial longitude observation when passing the Bahamas."

    Very interesting.

    And you wrote:
    "Now, to the most interesting part: Blue-4-5 and blue-4-1 as well as blue-4-6 and blue-4-8 seems to be Sumner lines, in each case the same observation is reduced using two different latitudes. These are some of the latest observations when the vessel was off the low shores of the Mississippi delta. I believe Sumner published his work first in 1843 so it fits in time, although I don't believe his method was very common as early as 1855."

    HOLY COW! Yes, indeed. Sumner's method is rarely attested in actual logbooks, at least on American merchant vessels, before the end of the century --even though the original book was published in 1843, as you've said. The method is a mere footnote in Bowditch in mid-century. This would constitute the earliest example I've ever seen of Sumner's method in actual practice making these bits of scrap suddenly ten times more interesting. I will look this over in more detail this evening since, if it's true (and I presume you are right), then it's definitely worth studying in finer detail. That's a great discovery you've made. :) You should consider writing it up as a paper. The Sumner procedure, also, of course, would explain why there are some calculations worked with integral values for latitudes. I should have spotted that sooner.


    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