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Re: Lunisolar Cycle Multiples of Short Lunar Cycle
by Karl Palmen
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Dear ELITE, Irv and Calendar People
Why would one ask, which one of these cycles is the most
accurate.
There is the implication that I should have listed just one
cycle (the most accurate).
I listed several cycles for the following reasons:
(1)
There is no consensus about which would be the most accurate
cycle (as shown in other notes)
(2)
There are criteria other than accuracy, such as shortness of the
lunar cycle or odd-number of years for Helios cycle.
This is also the approach I take in my lunisolar spreadsheets: http://www.the-light.com/cal/kp_Lunisolar_xls.html
.
Karl
From: East Carolina University Calendar discussion
List [mailto:CALNDR-L@...] On Behalf Of Irv Bromberg
Sent: 18 May 2009 15:05
To: CALNDR-L@...
Subject: Re: Lunisolar Cycle Multiples of Short Lunar Cycle
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.
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