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: GMT of lunar altitudes when possible?
    From: Brad Morris
    Date: 2019 Jul 8, 16:51 -0400
    Agreed John.  The Starpath article also makes that distinction.  Lunar Altitudes, not Lunar Distance.

    The question seems to be related to this article  https://www.starpath.com/catalog/accessories/starpilot/lun_alt.htm

    Wherein it is stated that "This one off by 9° worked fine. Practice with various conditions to see what the limits are."

    After reading the article, it appears as if Starpath is using the moon just as we would treat the sun in the AM or PM in a Time Sight.  That is, the moon is on or near our prime vertical.  The novelty of this method is the iteration of the inputs, altering the time until the cocked hat is small.  As the article states, this pre-supposes that your altitudes are nearly free from error.  The moon's altitude is notoriously troublesome, with the reflected light near but not at the horizon from the light of the moon.  That said, even the authors don't know how far off the PV the moon can be.  I suppose that's a function of your tolerance of time error.  

    I know this is going to sound slightly nutty, but if you did all of those iterations on the computer as shown and there were a few; why didn't you just read the time off of your computer?  Seriously, the time error corresponding to the oscillator drift of your computer's clock is going to be quite small comparatively! 

    Doing all those iterations by hand, alternatively,  seems to be error prone.  That would be complete with plotting exercises at each iteration.  

    I will wait for those more adept than I to rule on the relationship of angle from prime vertical to GMT time error.   That's my two cents from my armchair (Hahahaha).

    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