|
Sundial, calendar and Khmer temples
Prasat Sdok Kok Thom at Equinox
notes on astro-archaeology
''At the equinox, both gods and
demons see the sun in the horizon''
(Surya Siddhanta, chapter XII, verse 47)
|
Intro:
Between the solar-lunar events at Prasat Phanom Rung
14 days before and after equinox in spring 2009 I spent the time
doing field-research in the eastern provinces of Thailand, Prachinburi and Sra Kaeo. The area is geographically the western
part of the Cambodian plain and an amount of some 50 ancient Khmer
temples witness the prosperity of the former empire of Kambuja.
The temples span over an era from the 6th to 13th century.
The most magnificent Khmer sanctuary in the area is
Prasat Sdok Kok Thom (also transcribed as Prasat Sdok Kak Thom and
Prasat Sdok Kuk Thom) build in the 11th century.
The
temple also hosted the famous K. 235 inscription, dated by a
description of the location of the sun, the moon and the planets
when the main deity was installed.
|
 |
| |
|
Above: Central tower,
libraries and surrounding corridors.
Right: Plan of Prasat Sdok Kok Thom |
 |
| Courtesy to FAD for the plans
above. |
|
| |
|
|
ASTRO-ARCHAEOLOGY
Basic data for calculations on astro-archaeology
are:
1) location of the site, 2) orientation of the structure and
3)
date of the temple.
Further data for interpretation of orientation and
lay-out would include history, art-history, ethnography, religion,
linguistics, mythology, ancient astronomy/astrology etc.;
astro-archaeology is an interdisciplinary
study.
1.0:
LOCATION
The coordinates were determined on site by use of use of handheld GPS (Garmin
GPSmap 60CSx) in the central tower: N13.84356 E102.73729 (Datum: WGS 84).
|
 |
| (Try and copy/paste the coordinates
into Google Map, Google Earth or PointAsia and see the location from above) |
| |
|
2.0:
ORIENTATION
2.1: Compass
At a
visit to Prasat Sdok Kok Thom in 2004 compass readings indicated the orientation to
be nearly equinoctial: 89.5° - only ½° from equinoctial straight
east.
As the error-margin of compass readings is in the range of ± ½°
and magnetic deviation was not know for certain (-2.5° was used tentatively) the
site was expected to be orientated 90.0° true east.
Above: Prasat Sdok Kok Thom and its associated eastern barai (courtesy to
PointAsia).
2.2: GPS
GPS-measurements (waypoints and
tracks) were conducted in 2004, 2006 and 2009; all confirming the likeliness of
equinoctial orientation, 90.0° true east. The error margin of a handheld GPS is
app. ± ½° on structures larger than 100 m.
If a temple has long ceremonial walk-ways and/or a large
baray the error is reduced. The Sdok Kok Thom eastern baray is anyway not
included in orientation calculations because the exact location of the corners
could not be determined. The western and eastern moats are apparently orientated straight north-south;
the eastern corners of the eastern corners were troublesome due to erosion and
rumors about land-mines and robbers did not invite to full ground-truthing...
Above: GPS-map based on waypoints
and track-points.
.
Because compass-readings, GPS-measurements, and
satellite images all indicated an orientation close to or exact
equinoctial, I decided to let the
rising sun at equinox clarify the exact orientation. I therefore spent the early
mornings around spring equinox alone in the temple corridors hoping that the
eastern horizon would be without clouds giving opportunity to take photos of the
rising sun from the centre-line of the structure. The diameter of the sun
is app. ½° and solar observations/photos have an error-margin in
the range of less than ± 1/10°
2.3: Satellite images
| |
 |
|
| |
Above: Satellite image (courtesy
to PointAsia)
edited in a CAD-CAM program.
The yellow stippled line and the red full-lines are orientated 90.0°.
The dotted red line is orientated 89.5°.
The orientation of the ruin is apparently 90.0°
|
|
| |
 |
|
| |
Above: Satellite
image (courtesy to PointAsia) edited in a CAD-CAM program.
The landscape around Prasat Sdok Kok Thom is searched
for contours indicating an associated urban layout with similar
orientation as the temple, but without results (Inscription K.235 mentions that the
land belonging to the temple was marked towards north, south, east and
west). Red lines are orientated cardinal. The red rectangle is drawn
symmetrical around the centre-line of the sanctuary and its processional
path, showing that the baray has another centre-line.
The green stippled lines deviate 2.0° from 90.0°; the
yellow 3.6°. No ground-truthing was
conducted.
The red arrow marked '400 m north' shows the location
where Aymonier 100 years ago reported about an ancient road from Angkor. |
|
2.4: Solar observations
| Expectations /
calculations: Spring equinox
2009 was 20 March, 18:44 local time.
At sunrise the 20th the sun rose at an
azimuth a little more than 90.0° and rising towards south (see picture)
the sun would not be observable straight east.
The 21st the sun rose at 89°41' and was
calculated to be orientated straight east at 06.19 (see picture).
The horizon east of Prasat Sdok Kok Thom
is obscured by vegetation, which was reduced by cutting the day before;
but the local horizon was still more than altitude zero (sea-level), so
the best day to observe the sun was the 21 of March hoping than the sun
had ascended above the trees when passing straight east. |
Right: 21
March 2009
Below: 20 March
2009
 |
 |
 |
|
 |
| Above: First visibility
of the sun was at 06:20 |
|
Above: 06:21 the 21st
of March 2009 |
|
The orientation of the sun was calculated to be straight east at 06.19 -
soon after which the sun became visible; but it was not possible to take photos from the centre-line of the
door-ways! My experiences
from solar observations through the door-ways of Prasat Phanom Rung immediately told me that
the doors were not orientated straight true east and that the sun would be aligned with the centre-line of the door-ways the next
day.
|
 |
|
 |
|
 |
| Above: 06:36 the 21st |
|
Above: 06:57 the 21st |
|
Above: 07:16 the 21st |
|
The rays of the rising sun penetrating the door-ways of Prasat Sdok Kok
Thom do not reach and illuminate the linga in the central tower;
but this would not bother a God
residing in the sacred central room, the garbha-griha. Shiva
would know when the sun rises straight east marking the moment when the sun has
completed half of his travel from his southernmost to his
northernmost sunrise point - from winter solstice to summer solstice.
The garbha-griha has one open door and three doors
blinded by stones, but Shiva's 3rd eye would anyway be able to watch the sunset
through the western stone-door and watch the Northern Star through the
northern blind-door as well. The priests and other humans need an open door to serve the God.
The best sunrise observation point for photographers and other mortals
is at the lowest step of the staircase leading up to the God. From this
point there is app. 60 m to the easternmost door of the eastern
gopura.
There is only space for one observer, so if the locals
want to make the solar event at Sdok Kok Thom into a tourist show as at
Prasat Phanom Rung the only way to do so is by placing a video-recorder
at the lowest steps and use large monitors for the audience for watch
the sunrise.
NB: Actually the prasats are 'palaces of the gods'; not
showrooms for commoners. |
|
 |
| |
Above: 07:16 the 21st |
 |
|
 |
Above: The door-ways and
the processional pathway seen from 200 m east of the easternmost door.
The alignment follows the processional walk-way. |
|
Above: The door-ways and
the processional pathway seen from 200 m east of the easternmost door.
The alignment follows the doors. |
|
Comparing the two photos above it is evident that the
centre-line of the doors is not identical to the centre-line of the processional
walk-way!
If the door-ways are orientated 89.5° as
indicated by the solar observations above then the processional pathway
and the total structure of the temple is most probably orientated
90° true east.
|
Above:
The door-ways and the processional walk-way
before renovation and apparently aligned (!)
Photo: Courtesy to
Fine Arts
Department
2.5: Photo analysis:
Photo
analysis is based on perspective drawing where the extended contours of a
construction will meet in the perspective point.
If two or more door-ways have identical size, level and
centre-line, then the perspective lines will meet in the perspective point on the
local horizon of the construction (red lines on photos below). If the construction is build at sea-level and
orientated straight east the perspective point will be identical to the
equinoctial point: 90° true east and altitude zero.
A photo of the rising sun through a set of door-ways
(with identical size, level and centre-line) can give very exact information of
the path of the rising sun when analyzed in a CAD-CAM program. The diameter of the sun is close to 0.5° and can be used as a 'measure-stick'. If
the latitude of the location is known we also know the path of the rising sun
(90° minus the latitude) which can be drawn on the photo as done below (yellow
lines).
Following the path of the sun to the horizon we know where the sun rose and
simple astronomical calculation will tell the path of the rising sun the days
before and after the photo was taken.
This method has been used with success at
Prasat
Phanom Rung and other temples; but was not successful at Prasat Sdok Kok
Thom. The main reason is insufficient knowledge about the levels of the
door-ways. A second obstacle was that the door-ways are of different sizes and
apparently now sharing the same centre-line. A string or a lazer-light will
easily tell the centre-line at the next visit, but a full measurement of level
and orientation (as done at
Prasat Phu Phek)
will not be conducted.
 |
|
 |
| Above: The
perspective lines connecting the corners of the first and the last
door-way do not meet in the same point and pass the corners of the
door-ways between. |
|
Above: Sunrise
through the eastern gopura of Prasat Sdok Kok Thom the 21st of March
2009.
|
|
The perspective lines drawn on the photos do not meet in the same point, the perspective
point, which is marked by a green circle and tentatively placed on an
approximate horizon (blue line).
The yellow line with an arrow passing the centre of the sun depicts
the path of the rising sun and it is obvious that the sun rose very
close to the perspective point. The perspective point marks the
orientation of the door-ways and as the azimuth of the sun at sunrise
the 21st of Marsh was 89.67° the orientation must be a little more:
Measured on the photo in CAD-CAM and using the sun as 0.5° the addition
should be 0.06° indicating an orientation on app. 89.72° ~ 89.7°
The two yellow stippled lines on each side of the yellow arrow shows the
paths of the sun the day before (right) and the day after (left) the
22nd.
Right and below:
Sunrise through the gates of Sdok Kok Thom the morning after spring equinox 2009. |
|
 |
 |
|
 |
|
|
Summing up on the various ways
of determining the orientation of the
door-ways:
Compass (on centre-line): App. 89.5°
Solar observation: App. 89.5°
Photo analysis: App. 89.7°
Conclusion: The photo-analysis is the most accurate method, so the orientation
on the door-ways is app. 89.7°
The orientation
of the super-structure of Prasat Sdok Thom
is equinoctial: 90.0° true east
3.0: DATE of Inscription K.
235, stanza 123:
Prasat Sdok Kok Thom was consecrated the 8th of February 1053;
when Bhava was installed
(Billard).
|
Bhava is one of Siva's eight
forms (Śarva, Bhava, Paśupati, Iśâna, Bhîma,
Rudra, Mahâdeva, and Ugra). The eight-petalled lotus flower motifs frequently
used in Khmer art and architecture probably represent the 'total Shiva',
including all his aspects. At Sdok Kok Thom eight-petalled gold leafs were
excavated in the eastern gopura and at several levels between the
sand-stone blocks in the central tower, where they were deposited in the
cardinal directions.
The linga, symbolizing the Bhava aspect of Shiva, was installed on the
above date by performing a Brahmin ritual. The consecration was the final of
a series of Brahmin rituals. One of the first rituals would have been when the
master-builder or lord-of-the-cord would determined the orientation of
the temple by
means of the
Vedic Circle. |
|
| |
|
|
Most dated Khmer
inscriptions give a Saka year, a lunar month, the number of ascending or waning
day, and the weekday - or some of these data.
The two other dates mentioned in
Inscription K.235 mention year, lunar month, and ascending or waning day, from
which the Gregorian dates easily can be calculated:
D, 86: Saka 894, 3rd ascending day in the lunar month pausa = Wednesday
11 December 972
D, 90: Saka 901, 3rd ascending day in the lunar month pausa = Wednesday
24 December 979
The third date mentioned in K.235 gives the Saka year
and the horoscope
of the planetary positions when the deity was consecrated (right), which makes the
calculation more complicated. |
 |
3.1: Dating the
Inscription K. 235, stanza 123:
3.1.1:
Aymonier (1901, p. 52) was the first to
translate the famous K. 235 inscription of which stanza 123 was only partially
translated and the date given as Saka Era 974.
3.1.2:
Briggs (1951, p. 170):
AD
1052.
3.1.3:
Coedes and Dupont (1943, p. 156-154.): ... when ''the
sun and the other planets (respectively in) Aquarius, Virgin, Libra, Aquarius,
Aquarius, Pisces, Aquarius, Aquarius, and Pisces. The horoscope in Sagittarius. Bhava
was erected in the year marked by the (9) orifices, the (7) mountains and the
(4) Vedas.'' (my translation) => Saka Era
974.
3.1.4:
Billard: 8th of February 1053.
3.1.5:
Golzio (2006, p.
153): 1st of February 1051 AD at 06.00... - earlier dated to 8th of February 1053.
3.1.6:
Eade
(2006, p. 25 - 28): 8th of February 1053.
3.2: My attempt
on calculating the date:
3.2.1. Most translators of the Sanskrit text in stanza
CXXIII
agree on translating the Saka year as 974.
3.2.2. The Saka Era
started in 78 AD, so a (too) simple calculation is: Saka 974 = 1052 AD
(974 + 78).
3.2.3.
As the Saka year actually starts at new-moon before equinox
then Saka 974 is the period from the new-moon before equinox 1052 to new-moon
before equinox 1053 AD (sometimes written as March 1052 to March
1053).
Note:
If we
don't know whether Saka 974 is treated as an elapsed or a current year
the time-span of
Saka 974 is March 1051 to March 1053 AD. But because the two other dates
mentioned in inscription K.235 are treated as a
elapsed
years, we have good
reason to assume that Saka 974 is treaded as a
elapsed
year. (=> Saka 974:
March 1052 to March 1053).
3.2.4.
New moon before equinox:
Using Yano's
Pancanga:
1052 March 4 Wednesday, Saka 974, lunar month: Caitra,
Suklapaksa 1 (1st ascending day).
1053 March 23 Tuesday, Saka 975, lunar month: Caitra, Suklapaksa 1
(1st ascending day).
=>
Saka 974 spanned from Wednesday the 4th of March 1052 to Tuesday the 23rd of
February 1053 and the date of consecration is to be found between these two dates!
Note: If I use modern astronomical
parameters, I get the following incorrect dates:
True equinox in 1052 was 14 March and the previous new moon was 4 March. => 1st
ascending day = 5 March 1052.
True equinox in 1053 was 15 March and the previous new moon was 21 February =>
1st ascending day = 23 February 1052.
3.2.5. ''The sun ...''
The
inscription informs us that the time
of consecration was when ''the
sun and the other planets were (respectively in) Aquarius, ... '' and as the
sun passes Aquarius every year in January-February the date in question must be somewhere in January-February 1053 AD.
- so the year is 1053 AD.
3.3.6. ''... and the other planets''
The chronology of
'the other planets' would give us possibility for a more exact dating; but is not
explicitly given. If we assume that the chronology follows the order of
week-days ...
|
Weekday |
Sunday |
Monday |
Tuesday |
Wednesday |
Thursday |
Friday |
Saturday |
- |
- |
|
Deity |
Surya |
Chandra |
Yama |
Varuna |
Indra |
Kubera |
Agni |
Rahu |
Ketu |
|
Planet |
Sun |
Moon |
Mars |
Mercury |
Jupiter |
Venus |
Saturn |
Rahu |
Ketu |
|
Zodiacal sign -
Coedes |
Aquarius |
Virgo |
Libra |
Aquarius |
Aquarius |
Pisces |
Aquarius |
Aquarius |
Pisces |
...
we get the following relations: Sun in Aquarius, Moon in Virgo, Mars
in Libra, Mercury in Aquarius, Jupiter in Aquarius, Venus in Pisces, Saturn
in Aquarius, Rahu in Aquarius, Ketu in Pisces - and can start searching for
when such a horoscope happened.
Note:
Of the above nine 'planets' we nowadays only count the five in the middle;
which are visible by the naked eye.
3.3.7.
The moon in Virgo
The moon is the 'planet' which as seen from the Earth moves the fastest and is
the first to be checked in order to restrict our search:
A easy-to-use desktop astronomy program (a desktop planetarium with modern
parameters) as for example Cybersky gives the moon to enter Libra at app. 16.00 the 6th of February
and exit the 8th at app. 21.00 => further search is restricted to the 6th to
8th of February 1053. With this time limit we have to check the Pancanga
and HIC to see the results of contemporary Siddhantas (see 3.3.9.).
3.3.8.
Mercury, Venus, Mars, Jupiter and Saturn
The desktop planetarium gives the five visible planets
to be in the same zodiacal sign the 6th, 7th and 8th of February 1053:
|
Planet |
Sun |
Moon |
Mars |
Mercury |
Jupiter |
Venus |
Saturn |
Rahu |
Ketu |
|
Zodiacal sign -
Coedes
|
Aquarius
|
Virgo
|
Libra
|
Aquarius
|
Aquarius
(kuca = Gemini) |
Pisces
|
Aquarius
|
Aquarius
|
Pisces
|
|
Zodiacal sign -
Modern |
Aquarius |
Virgo |
Scorpio |
Pisces |
Gemini |
Aries |
Pisces |
? |
? |
Note:
None of the planets are in the zodiacal signs as given by Coedes (!). All are
in the following zodiacal sign, except Jupiter. The latter is four signs
ahead, which is due to the translation of the Sanskrit text, where the sign
not specifically is given as Aquarius, but
poetically is referred to as kuca ('female breasts'). Following Dr.
Eade's interpretation (2006, p. 26) of kuca as Gemini (twins) then Jupiter was
located as written in the inscription.
The four other planets - except Mercury - are in the first quarter of the
following sign, indicating that
our assumption that the chronology of the planets follows the order of
week-days (3.3.6.) is correct - and that our parameters for calculating are
incorrect. We therefore skip modern parameters and turn to Siddhantic parameters
on astronomy.
We know of Siddhantas (canonical text-books) of
which the Surya Siddhanta was widely used in SE Asia (Eade, p. ) and
to some extend still is in modern India. The parameters given in the Surya
Siddhanta have been computerized and are available as Siddhantic programs
like
HIC and
Pancanga
3.3.9.
Siddhantic programs on ''the sun and the other planets ...''
3.3.9.1.
Pancanga
The Pancanga gives the moon to be in Libra on the 8th and 9th
of February 1053. As Mercury is given to be in Aquarius the 8th and be in
Pisces the 9th. the latter date is excluded. All other planets do not change
sign from the 5th to the 11th.
The Pancanga locations of the planets are added to the
table below and there is a clear accordance between Coedes translation and
the Pancanga: The only discrepancy is the location of Rahu. The date of the
horoscope is 8 February 1053.
3.3.9.2.
HIC
HIC gives the moon to be in Libra on the 8th and 9th February 1053.
Mercury is given to be in Aquarius the 7th and be in Pisces the 8th. All
other planets do not change sign from the 7th to the 10th.
The HIC locations of the planets are added to the table
below. Again there is a significant accordance between translation and the
computer out-put - except for Mercury. The date of the horoscope is 8 - 9
February 1053.
|
Planet |
Sun |
Moon |
Mars |
Mercury |
Jupiter |
Venus |
Saturn |
Rahu |
Ketu |
|
Zodiacal sign -
Coedes
|
Aquarius
|
Virgo
|
Libra
|
Aquarius
|
Aquarius
=> Gemini |
Pisces
|
Aquarius
|
Aquarius
|
Pisces
|
|
Zodiacal sign -
Pancanga |
Aquarius |
Virgo |
Libra |
Aquarius |
Gemini |
Pisces |
Aquarius |
Gemini |
? |
|
Zodiacal sign -
HIC |
Aquarius |
Virgo |
Libra |
Pisces |
Gemini |
Pisces |
Aquarius |
? |
? |
|
Zodiacal sign -
Modern |
Aquarius |
Virgo |
Scorpio |
Pisces |
Gemini |
Aries |
Pisces |
? |
? |
|
Above:
Table comparing computer outputs on 8th February with Coedes' translation of
K. 235. |
| |
|
Comments:
|
|
| I:
|
There is a significant discrepancy between the computer output based on
modern astronomical parameters and the inscription, demonstrating that
datings of ancient Khmer inscriptions should be based on contemporary
parameters as given in the Indian siddhantas. |
| II:
|
There is a significant correspondence between the Pancanga / HIC and the
translation. |
| III:
|
The Pancanga out-put gives one date: 8th February. |
| IV:
|
The HIC out-put gives two dates, the 8th or 9th February; both with
Mercury located in the neighboring sign.
|
3.3.10.
"The
horoscope in Sagittarius"
This last information
informs us about the
time of the day when the consecration ceremony was performed: when Sagittarius rose on the
eastern horizon (... with Sagittarius in the ascendant).
Time = ?
I don't (yet) know how to deal with ascendant in the programs based on
Siddhantic parameters. A planetary program would easily tell when
Sagittarius rose on the eastern horizon, but the information is irrelevant
if we want to know how the ancient calendar makers conceived.
|
3.3.11. Conclusion on date of
consecration:
8th of February 1053.
For a more thorough examination of the dating, see
1051,
1052 or 1053?
|
 |
4.0.
|
CONCLUSIVE REMARKS ON ASTRO-ARCHAEOLOGY
|
4.1.
|
The temple is like the
majority of Khmer Hindu temples equinoctially orientated: The
azimuth = 90.0° true east,
implicating that the sun
rose and still rises aligned with the structure around true equinox in March and
September. |
| 4.2. |
The orientation of the temple is not related to the consecration date
of the linga. |
4.3.
|
The consecration date
and moment is inscribed as a horoscope and chosen due to
considerations about some kind of auspiciousness, the nature of
which we do not have any clues. |
LITERATURE
|
|
| Aymonier, E.: |
Khmer
Heritage in the Old Provinces of Cambodia, Paris, 1901. |
| Briggs, L.P.: |
The
Ancient Khmer Empire, Washington, 1951. |
| Coedes, G. and Dupont, P.: |
Les
stèles de Sdŏk Kăk Thom, Phnom Sandak et Práh Vihăr”, BEFEO
XLIII, 1943. |
Golzio, K.H.:
|
Chronologie der Inschriften Kambojas. Verifizierung und Umrechnung
von Datumsangaben der Śaka-Ära. Weisbaden, 2006. |
Eade,
J.C.:
|
Computers
vs Tables, Billard vs Golzio: Two new date-lists of the inscriptions
of Kamboja, Canberra, 2006. |
Burges, Ebenezer
|
Surya-Siddhanta . A Textbook of Hindu Astronomy.
India, 1858. (From: Journal of the American Oriental Society, Vol.
6, 1959-60. Page 141-498) |
| K.235 online |
In Thai
จารึกสด๊กก๊อกธม ๒
จารึกสด๊กก๊อกธม ๑ |
| K.235 online |
In French
|
| K.235 online |
In English:
http://instruct1.cit.cornell.edu/courses/hist190/Cambodia.html
Cornell University. |
| |
|
| PROGRAMS: |
|
|
| Yano, M and Fushimi M. |
Pancanga:, version 3.13. On-line |
Siddhantic parameters |
| Gislen, L. and Eade, J.C. |
HIC:
version 1.0. Free downloadable |
Siddhantic parameters |
| Ott, R.C. |
Astronomic Clock
version 10 |
Modern parameters |
| Schimpf, M.S. |
Cybersky Version 4.0.6.
Planetarium |
Modern parameters |
Above: 'GPS-reference point' 2002 at Prasat Sdok Kok Thom.
The compass shows magnetic north, the N-arrow depicts true north.
The difference is called magnetic deviation, which depends on
location.
At Prasat Sdok Kok Thom the magnetic deviation is approximately 2°
(!).
If the compass is not influenced by
metal hidden in the concrete
then the modern GPS-reference point is orientated incorrect
and the ancient Khmer master-builders more skilled
than modern high-tech constructers
not using the sun
INDEX
24 April
2009 © Asger Mollerup
macsida@thai-isan-lao.com
www.thai-isan-lao.com
โดย อ.ทองคำ |
