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
    Computing eclipses of Galilean satellites
    From: Andreas K
    Date: 2014 Feb 17, 10:04 -0800

    Dear members,

    for several days I try to compute the time of eclipses of the Galilean satellites to complete my own Nautical Almanac in the old style (before 1835). For all computations I use Jean Meeus, Astronomical Algorithms 2nd edition. So I started with Io and for a first attempt I omitted DT (ca.69sec) and use a mean value for the semiduration of 1h06m30s (can only be 2.5 minutes off the truth). For the first emersion this month I find in the www the data: 2014 Feb. 1, 15:58:12 ut.
    The formulae: longitude=163.8067+203.4058643d, gives for the superior conjunction (longitude=180°) the ut 13:32:11. The main perturbation by Europa caused a correction of -35 sec. So the time is 13:31:36. Adding the light-time (distanc Jupiter-Earth 4.33au=36m02s) and the semidu. I finally get 15:14:08. That’s 44 minutes off the correct time! I checked the algorithm for higher accuracy given by Meeus but can’t find any effects that can cause such a great difference. Can anyone help me? What I am doing wrong or what are my false assumptions?
    Every hint or suggestion is highly appreciated!

    Kind regards from Hamburg

    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com

    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