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: Old style lunar
    From: Ken Muldrew
    Date: 2004 Dec 15, 11:37 -0700

    On 15 Dec 2004 at 12:39, Alexandre Eremenko wrote:
    > Why did not he measure altitudes?
    With a sextant and an artificial horizon one can only measure altitudes up
    to 60?. That is enough for this series, and probably many more, but
    Thompson (and his contemporaries) never measured altitudes. It just wasn't
    part of their procedure.
    > Could you also explain the notation: what is TA and what's AA?
    True Altitude (TA) and Apparent Altitude (AA)
    > And what are the numbers
    > +3'48", -4', +2"
    These are the three corrections for clearing the lunar distance given by
    Witchell's method.
    > >perhaps one could work
    > >backward from his calculated altitudes to get the DR position.
    > Perhaps. For this we need to know the time
    > used in his alt calculations, and the equation of time
    > from his almanac.
    The average time for his lunar distance (given at the bottom of the series
    of each) is the time used for his altitude calculation. The equation of
    time is given in the almanac data for the sun (near the bottom of the post
    - 12:24.6 on the 26th and 12:05.0 on the 27th).
    > I suppose it was 9:03:45 for Altair and 9:12:47
    > (P. M. ?!) local time.
    Ken Muldrew.

    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