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
    Simultaneous near limb - far limb lunars
    From: Tibor Miseta
    Date: 2020 Oct 25, 03:01 -0700

    Dear NavList members,

    I joined this community a year ago, and among other sources I learned a lot from here. Thank you for sharing your invaluable knowledge and experience here!

    I am just a celnav hobbyist (completly landlocked :-( ) and recently started to be interested in "longitude by lunars". I developed my skills and knowledge (mainly thank to Frank's lunars pages and Henning Umland's book), and can peform quite good lunar distance observations.

    On Friday I went out for practicing and beside the Moon both Mars and Jupiter were visible. Mars was roughly 75° on the left side of the Moon while Jupiter 12° on the right. Just for fun I measured them one after the other and got two acceptable results for my watch error. (My watch was on porpuse off from UTC by roughly two minutes.)

    But then I had an idea, averaged the two results, and it was a big surprise: I almost received exactly my actual watch error (with only one second difference).

    I thought that the biggest error in the measurement is with my vision of matching the limb with the star/planet. This may be systematic and with a near limb - far limb comparison  this error may be cancelled out. And other systematic errors might be canceleld out as well: like the error in determining the Moon's semidiameter, parallax in azimuth caused by the oblateness of the Earth, delays in the measurement of time.

    Is this (almost) simultaneous near limb - far limb lunar observation is really a good (and may be known for others) method for fine adjustment of longitude by lunars? Or is it just a coincidence and I was extraterrestially :-D lucky last Friday night? (Since then it's cloudy, I couldn't make a control measurement.) And if so, what level of accuracy may be expected or usual?

    I attach my calculation for reference.

    Regards: Tibor

    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