NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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
Andreas
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