At another site, where I also posted my first post in this thread, someone pointed me at some typo's I made: I had used 'Winter Equinox' whereas it should've been 'Winter Solstice' ofcourse, and 'full moon' in stead of 'new moon'. Fortunately, I did use the correct date of this year's last new moon of Autumn in my calculations.
I'll correct the typo's in a minute
- Earendilyon