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
    Lewis and Clark lunars: 1803 Almabnac data
    From: George Huxtable
    Date: 2004 Apr 12, 19:01 +0100

    With the data from the 1803 almanac (copied again below), I forgot to
    include positions for Aldebaran and Regulus.
    These weren't taken from the 1803 almanac (I don't think star data was
    included in the almanac then) but were instead extrapolated backwards by 60
    years, to the start of 1804, from an 1864 almanac that I have. They agree
    with predictions (with rates of change) extrapolated forward from 1765,
    from the first edition of Maskelyne's "British Mariner's Guide".
    Unlike the star positions in a modern almanac, which are provided at 3-day
    intervals to 0.1 arc-minutes, these are only mean positions of stars,
    allowing for precession and (where applicable) proper motion, but
    neglecting aberration and nutation. As a result, they are only good to the
    nearest 0.5 arc-minutes or so.
    Aldebaran. Right Ascension  66deg 10.3' or 4h 24m 41s; Declination N16deg 06.3'
    Regulus.   Right Ascension 149deg 28.8' or 9h 57m 55s; Declination N12deg 55.2'
    Below, that earlier message is repeated.
    Relevant to those 1803 lunar distances by Lewis and Clark.
    I can quite some relevant extracts from the 1803 Nautical Almanac that I
    jotted down at my last library visit-
    Astronomical times and dates, of course, starting at noon each day, 12
    hours after the start of the civil day with the same name and date.
    All times Greenwich Apparent time.
                     RA             Dec        EOT (sub)
    2 Dec noon  16h 30m 54.1s  S21deg 53' 08"  10m 33.7s
    3 Dec noon  16h 35m 13.9s  S22deg 02' 07"  10m 10.5s
    2 Dec midnight 127deg 24'  20deg 05'
    3 Dec noon     133deg 54'  17deg 50'
    3 Dec midnight 140deg 08'  15deg 25'
    Lunar distances.
                    Aldebaran West   Regulus East    Sun East
    2 Dec midnight   58deg 00' 46"  22deg 19' 53"
          XV hrs     59deg 37' 27"  20deg 41' 16"
       XVIII hrs     61deg 13' 48"  19deg 03' 06"
         XXI hrs     62deg 49' 50"  17deg 25' 23"  120deg 36' 21"
    3 Dec  noon      64deg 25' 31"  15deg 48' 08"  119deg 06' 46"
         III hrs     66deg 00' 52"                 117deg 37' 33"
    No doubt you're aware that EOT (Equation of Time) was then defined in the
    opposite way than we do it now.
    If there's anything else that anyone would find useful, I will note it down
    at my next visit.
    contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

    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