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
    Longitude Sight, South Pacific, 1864 - Revisited
    From: Henry Halboth
    Date: 2018 Jun 26, 21:33 -0400
    To all,
    I have been fiddling with the subject sight since it appeared on NavList and, as a matter of general interest, have decided to publish the results of my fiddling. The Time Sight provides a perfectly valid solution of the astronomical triangle as employed in celestial navigation and has the further potential advantage of providing a purely mathematical solution to position finding without the need of resorting to the plotting of lines of position, althouh it is also quite adaptable to this later procedure. To illustrate how it was employed in line of position navigation I have recalculated the sight utilizing the more modern cosine-haversine formula and have included an azimuth calculation to facilitate the plotting of a line of position through the position demonstrated by the assumed Latitude and the determined Longitude - the so called tangent method, as opposed to the chord method whereby two separate postions are calculated and the line connecting them considered the LOP. The tangent method was employed at least throughout WWII, and favored by the Steamboat Inspectors on License Examinations. I have also calculated the intercept, utlilizing the Marc St Hillaire method to show the close agreement in the LOPs determined as between the two (2) methods. As I have no idea as to the height of eye aboard the Morgan I hae simply employed the altitude correction originally utilized in the calculation provided by Frank.
    For anyone interested in the determination of position without the need for plotting LOPs, I suggest looking into the use of the Time Sight in conjunction with 1) Latitude by Moon, Venus, or Star Meridian Transit with Longitude by Time Sight, 2) Use of the so called "back and fill" method, wherein a morning Time Sight is taken and not worked until a Noon Latitude is obtained and corrected for the distance run or difference in Latitude between the sight times and the AM sight, as obtained by use of the Traverse Table, then worked using the more correct Latitude, or 3) Simply employing the Longitude Factor, as obtained from Table 35, of Bowditch, which see for full instruction.

    I do hope that I have not made too many typos in the attachments.

    File: 142300.marc-st-hilaire-position-line.odt
    File: 142300.time-sight-5.doc
    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