some astronomical definitions

[Guest guest]

Dear Bhagavathas,

 

Since I grappled with this problem for quite a while, please

allow me to clarify some basic astronomical points and also

as to how the panchangam arrives at the date for various functions.

 

____________

Defintion of DAY: sunrise to next sunrise.

 

A day will normally not equal 24 hours. it will be longer

than 24 hours during from june to jan and shorter than

24 hours from jan to june.

clearly, this will depend on place.

 

Defition of Thithi: The PHASE OF THE MOON.

 

THIS DOES NOT DEPEND ON WHERE YOU ARE ON EARTH.

The time new moon starts and ends, or full moon

starts and ends is INDEPENDENT OF where you

are located on earth,

 

as THE PHASE OF THE MOON IS DEPENDENT ONLY ON

THE RELATIVE POSITIONS OF THE SUN, EARTH AND

THE MOON.

 

note that moonrise and moonset times are different

in different places on the earth.

 

DEFINITION OF NAKSHATRAM:

 

Imagine the earth's equatorial plane projected out

into space infinitely. This is defined as the CELESTIAL

EQUATOR.

 

Take the projection of different star constellations

onto this celestial equator. Using the center of the

earth as the reference point, you can draw a celestial circle

and divide it into angles of 13 degrees and 20 minutes each.

Each of these correspond to one star constellation.

 

At any time, the projecton of the MOON onto this celestial

equator will fall into one of these constellations.

At any given point of time, this constellation is

defined as the NAKSHATRAM.

 

The NAKSHATRAM AT A GIVEN INSTANT OF TIME

IS ALSO INDEPENDENT OF WHERE YOU ARE LOCATED

ON the earth

 

as it also depends ONLY ON THE RELATIVE

POSITIONS OF THE MOON AND THE EARTH. (the stars

are fixed as they are at infinity, our calender

system is based on the fixed stars, hence termed

SIDEREAL system)

 

These celestial events happend at day and at night

in both india and us.

 

However, what the panchangam does is to apply

decision rules on the day and time to

perform various rituals

 

Based on the actual times of occurence

of the celestial event.

 

For example, a simple decision rule could be

that Do ritual A on Second Panchami of month. If

Panchami exists over two different days,

do ritual A on day where it exists for more

time.

 

Let me give actual numbers to this example.

 

Using data on Purattasi of this year from Pambu

Panchangam. Second panchami falls on Oct 7.

The panchangam has entry Panchami 39-14.

This entry refers to the ENDING TIME of

panchami.

 

39-14 means 39 Naazhi, 14 Vinaadi.

 

If we look at the correspondind ending

time for chaturthi on the previous day,

we find that previous ending time is

40-48.

 

Since a day has 60 Naazhigai, and each

naazhigai has 60 vinaadi, on the

previous day, panchami exists

for 19-12 (subtract 40-48 from 60-00)

(in india, on oct 6)

 

Therefore, the panchangam people (using

the previously mentioned decision rule)

would ask you to perform ritual A on

Oct 7 (as 39-14 on Oct 7 is greater

thatn 19-12 on Oct 6).

 

Now, lets come to the US.

 

First, we need to calculate the exact time

of ending of chatruthi and panchami in

terms of US time. As explained previouly,

these times are independent of the place

where you reside.

 

Panchami ends Thanjavur sunrise time on

Oct 7 + 39-14.

 

Sunrise time on Oct 7 = 6.02 am.

(sunrise times may differ from other

sources, use US naval lab data)

 

First, convert 39-14 into hours.

 

39-14 = (39+14/60) naazhi

= (39+14/60)/60 days

= (39+14/60)*24/60 hours

= 15.69 hours

= 15:42 (15 hours, 42 minutes)

 

Therefore, panchami ends IST 06:02 + 15:42

= 21:44

 

This time corresponds to 21:44 - 09.30 = 12:14 EST

= 09:14 Pacific

(both of Oct 7)

 

Now, we need to figure out of panchami exists for more

time on Oct 7 or Oct 6 for US time.

 

Using the previous method, we can figure out that

Chaturthi ends on IST 06:02 + 40-48 = 06:02 + 16:19

= 22:21 IST Oct 6

= 12:51 EST Oct 6

= 09:51 pacific Oct 6.

 

Since sunrise around this time is in both regions will

be between 05.00 am and 07.00 am in both regions local time,

it is clear that from sunrise Oct6 to sunrise oct 7,

panchami exists for a greater time on OCT 6 in

all parts of the US. for EST, panchami exists for

about 6 hours after Oct 7 sunrise while it exists

for about 18 hours after Oct 6 sunrise.

 

 

Therefore, ritual A SHOULD BE DONE ON OCT 6 in the

US.

 

Therefore, in order to find the appropriate dates

to perform various rituals, ONE NEEDS TO KNOW THE

DECISION RULES THAT ONE'S SAMPRADAYAM USES

TO DECIDE ON THE DATES.

 

In general, using the same offset in india

as in the Us will result in error many time.

(for tarpanams, i find that dates are different

in the US than in India about 50% of the time)

 

Hope the above is of some help to at least

a few people. Sorry for the long e-mail.

 

Anand