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
    Ex-Meridian Sight using Inmans
    From: David C
    Date: 2020 Jun 10, 03:01 -0700

    Although it is just under two weeks to the winter solstice today was a perfect day for CN. The sky was blue, there was absolutely no wind and the temperature was a comfortable 14°C.  I took a few practice sights using the anti-spoof app and also took a noon sight. Rather than work the noon sight or calculate intercepts for the other sights I decided to  reduce an early PM sight by the ex-Meridian tables in Inmans (1932).

    The meridian altitude was  51° 19' in an AH.

             51°   19'

           IC       -4

              51 15

    /2  25 37.5

    SD/R    +14.1'

    Ho = 25°   51.6 '   ----noon altitude

    The PM sight was  UT 01 05 46     49°  30' 50"

    Following the  procedure above ho = 24°  57.5'    --------PM sight

    Now calculate apparant time

    DR long = 175° 05.2'

    UT 01 05 46

                       195°  08.1'

    increment        1°   26.5'

       GHA         196° 34.6'

    Add E long   175°  05.2'

         LHA          371°  39.8'

                       - 360°

                           11°  39.8'

    Inmans does nor have an arc to time table so I used Norie.......

       Apparant time 0h 46m 40s  PM

    Time of noon was 01 05 46    -  0h 46m 40s  = 00 19 06 which agrees with app on my phone.

    Now calculate ex=meridian correction....

    Table 1  9.888

    Table2   8.009

    Sum     17.897

    From Table 3 correction = 54.2'

    A second correction from table 4 is -0.2' so the correction is 54'

    Finally compare the calculated correction with the actual

      ho noonsight - ho pm sight  =  54.1'

    This remarkable agreement suggests either luck or that my errors are systematic, not random, and that they cancel out on subtraction of the two altitudes!






    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