On 2009 May 18, at 04:05 , Palmen, KEV (Karl) wrote:
ELITE wrote: But which cycles are the most accurate in terms of lunation period and mean year compared to the mean solar year (365.242 189 67 days (365 d 5 h 48 min 45 s)) and the mean lunation period (29.530589 days (29 d 12 h 44 min 2.9 s)) (correct me if I have the mean solar year/syndonic month slightly off)?
Karl says: This is a question that is meaningful only if you make the incorrect assumption that these values are constant. Why does he ask this question?
Irv replies:
My previous message in this thread discussed the accuracy of his proposed solar year and lunation period.
ELITE perhaps assumed that the values are constant, but even though the values vary it is easy to answer his question, just by evaluating the appropriate lengths relative to the changing astronomical lengths. The easiest way to carry out a solar and lunar astronomical drift analysis, if I do say so myself, is using my "Solar_Calendar_Drift" spreadsheet at:
and my "Lunar_Calendar_Drift" spreadsheet at:
as I cited previously in this thread.
The solar spreadsheet uses actual SOLEX-integrated equinox and solstice moments (listed at one-century intervals).
The lunar spreadsheet uses my mean lunation polynomials from <http://www.sym454.org/lunar/> which were fitted to SOLEX-integrated lunar conjunction moments. The SOLEX integrations were carried out in terms of Terrestrial Time (atomic time).
For conversion to mean solar time both spreadsheets use Meeus-Espenak Delta T expressions from the NASA Eclipses web site.
Both are open source.
-- Irv Bromberg, Toronto, Canada
