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: Lewis and Clark lunars: more 1803 Almanac data
    From: Frank Reed CT
    Date: 2004 Apr 16, 16:44 EDT
    Ken M wrote:
    "If we consider the two series with Aldebaran (A and C in your original message) as one series, then a least-squares fit gives an apparent motion of the moon of 0.239°/hr. The almanac data shows that the moon had an apparent motion with respect to Aldebaran of 0.534°/hr during that interval."

    The rate in the almanac data is geocentric. You would have to calculate the apparent topocentric rate incorporating changing parallax and refraction in order to compare against the observed rate.

    "It's pretty hard to misidentify either Aldebaran or Rigel."

    Although I don't think one can reach the conclusion that they misidentified their star *yet*, it is a real possibility. For anyone trained in celestial navigation in the past 75 years identifying the stars is part of the game. But back then it wasn't. Stars were rarely used by navigators in the 19th century *except* the nine lunars stars. Bowditch and other navigation manuals included little charts and descriptions for these stars and no others. Certainly many people learned the constellations for their own amusement, but those who did not would have a tough time picking out the right stars until they accumulated some serious experience.

    Frank E. Reed
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
    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)