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Re: Ekadasi, panchangam questions

From: Martin Gansten (mgansten_at_sbbs.se)
Date: Sat Feb 06 1999 - 00:22:47 PST

Without being a "panchangam expert", I would like to make a couple of points
here, subject to correction by those more learned:

>The
>phase of the moon should be the same at any given
>time anywhere in the world.  

This is not strictly correct. Due to the closeness of the Moon to the Earth,
the longitude of the Moon as simultaneously observed from various points on
the Earth's surface (such as Chennai vs Chicago) may vary by up to 2
degrees. This phenomenon, known as lunar parallax, would cause the start/end
time of a given tithi or nakshatra to vary by up to 4 hours. However, modern
astronomical tables do not generally take this so-called topocentric
calculation into consideration, but use geocentric formulas instead,
calculating the position of the Moon as it would be seen from an imaginary
point in the Earth's centre. Panchangas relying on such formulas would show
uniform start/end times of tithis and nakshatras for different locations,
differing from observable fact.

>  1) Does this mean that if Ekadasi ends in the morning
>     according to the Indian panchangam, in the U.S.,
>     we should observe Ekadasi the date before? What is
>     a general principle to follow to account for the
>     time difference?

The idea, so far as I understand, is always to observe the relationship
between the day (vaara, as defined by sunrise etc) and tithi at one's place
of residence.
 
>  2) What is the definition of Ekadasi for Sri Vaishnavas?
>     Is it the percentage of moon illuminated, or number of
>     days in a paksha? 
>     I know it is different from smArtas, but in what way?

I believe the definition is universal: a tithi is the time it takes the Moon
to move 12 degrees farther away from the Sun. The difference lies, I think,
in different rules for how to relate tithi to vaara, when one day is touched
by two or more tithis.

The above hopefully answers your 3rd and 4th questions as well.

Adiyen Ramanuja dasan,
Martin Gansten