EXPLORING THE FIRST SCIENTIFIC OBSERVATIONS OF LUNAR ECLIPSES MADE IN SIAM

Abstract

The first great ruler to encourage the adoption of Western culture and technology throughout Siam (present-day Thailand) was King Narai, who also had a passion for astronomy. He showed this by encouraging French and other Jesuit missionaries, some with astronomical interests and training, to settle in Siam from the early 1660s. One of these was Father Antoine Thomas, and he was the first European known to have carried out scientific astronomical observations from Siam when he determined the latitude of Ayutthaya in 1681 and the following year observed the total lunar eclipse of 22 February. A later lunar eclipse also has an important place in the history of Thai astronomy. In 1685 a delegation of French missionary-astronomers settled in Ayutthaya, and on 10 –11 December 1685 they joined King Narai and his court astrologers and observed a lunar eclipse from the King's ‗country retreat' near Lop Buri. This event so impressed the King that he approved the erection of a large modern well-equipped astronomical observatory at Lop Buri. Construction of Wat San Paulo Observatory—as it was known—began in 1686 and was completed in 1687. In this paper we examine these two lunar eclipses and their association with the development of scientific astronomy in Siam.

Full text

Journal of Astronomical History and Heritage, 19(1), 25–45 (2016).
Page 25
EXPLORING THE FIRST SCIENTIFIC OBSERVATIONS
OF LUNAR ECLIPSES MADE IN SIAM
Wayne Orchiston, Darunee Lingling Orchiston
National Astronomical Research Institute of Thailand, 191 Huay Kaew Road,
Suthep District, Muang, Chiang Mai 50200, Thailand.
Emails: wayne.orchiston@narit.or.th
Martin George
National Astronomical Research Institute of Thailand, 191 Huay Kaew Road,
Suthep District, Muang, Chiang Mai 50200, Thailand, and University of
Southern Queensland, Toowoomba, Queensland, Australia.
Email: martingeorge3@hotmail.com
and
Boonrucksar Soonthornthum
National Astronomical Research Institute of Thailand, 191 Huay Kaew Road,
Suthep District, Muang, Chiang Mai 50200, Thailand.
Email: boonrucksar@narit.or.th
Abstract: The first great ruler to encourage the adoption of Western culture and technology throughout Siam
(present-day Thailand) was King Narai, who also had a passion for astronomy. He showed this by encouraging
French and other Jesuit missionaries, some with astronomical interests and training, to settle in Siam from the early
1660s. One of these was Father Antoine Thomas, and he was the first European known to have carried out
scientific astronomical observations from Siam when he determined the latitude of Ayutthaya in 1681 and the
following year observed the total lunar eclipse of 22 February. A later lunar eclipse also has an important place in
the history of Thai astronomy. In 1685 a delegation of French missionary-astronomers settled in Ayutthaya, and on
10–11 December 1685 they joined King Narai and his court astrologers and observed a lunar eclipse from the King‘s
‗country retreat‘ near Lop Buri. This event so impressed the King that he approved the erection of a large modern
well-equipped astronomical observatory at Lop Buri. Construction of Wat San Paulo Observatory—as it was
known—began in 1686 and was completed in 1687. In this paper we examine these two lunar eclipses and their
association with the development of scientific astronomy in Siam.
Keywords: Siam, King Narai, lunar eclipses, Ayutthaya, Jesuit astronomy, Lop Buri, Wat San Paulo Observatory
1 INTRODUCTION
The Jesuits are an order of the Roman Catholic
religion with a long tradition in science, and
especially astronomy (Udias, 2003). While the
astronomical activities of European Jesuits in
Beijing during the seventeenth century are well
known (e.g. see Needham, 1959; Pigatto, 2004;
Udias, 1994), few astronomers are aware that
French Jesuits triggered the emergence of
scientific astronomy in Siam (present-day Thai-
land) and India (see Kochhar, 1991; Rao et al.,
1984) during this same century.
Jesuit astronomers were responsible for the
first scientific astronomical observations made in
Siam, in 1681–1682 and 1685, and in each in-
stance a total lunar eclipse was involved. This
paper examines these two events, and forms
part of a larger research project that is described
in Orchiston et al. (2016b).
But before we examine these eclipses we
should meet King Narai who was largely respon-
sible for the introduction of scientific astronomy
in Siam.
2 KING NARAI: A BIOGRAPHICAL SKETCH
One of the most revered of Thailand‘s historic
rulers, ‗King Narai the Great‘ (Figure 1) was
born in 1633 and died prematurely on 11 July
1688. He was the fourth king to rule during the
Prasat Dynasty, which was the fourth of the five
Dynasties of the Ayutthaya Kingdom (see Table
1). Narai became the King of Ayutthaya in 1656,
when just 23 years of age, and remained on the
Figure 1: A contemporary French sketch of King Narai
dressed in Persian attire (en.wikipedia.org).

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 26
Table 1: Thai kingdoms and dynasties. King Narai ruled dur-
ing the Prasat Dynasty.
Kingdom
Duration
(years AD)
Dynasty
Sukhothai
1238–1438
Ayutthaya
1350–1767
Uthong
Suphannaphum
Sukhothai
Prasat
Ban Phlu Luang
Thonburi
1767–1782
Rattanakosin/
Thailand
1782–
throne until his death. Upon his succession King
Narai
... inherited a large and powerful kingdom in
the centre of mainland South-East Asia. His
realm reached south to the kingdoms of Pat-
tani, Ligor, Phattalung and Songkhla; in the
east Cambodia had acknowledged Ayutthaya‘s
suzerainty, and in the west the port of Tenas-
serim on the Bay of Bengal was under Thai
control. (Hodges, 1999: 36; for Thai localities
mentioned in this paper see Figure 2).
Despite his comparative youth, from the start
King Narai was an astute politician and a skilled
military strategist. To stabilize the political en-
vironment in northern Siam he occupied Chiang
Mai in 1662 and later that year and in 1663 he
occupied parts of present-day Myanmar in order
to pre-empt a Burmese invasion of Siam. How-
ever, his troops subsequently abandoned both
Figure 2: A map showing Thailand localities mentioned in
the text (map: Wayne Orchiston).
regions and concentrated on consolidating their
military presence in the Ayutthaya-Lop Buri-
Bangkok area. Towards this end, forts designed
by French engineers were erected in these cities
and other cities in Siam.
King Narai also was very active in internation-
al affairs, and he saw exposure to Eastern and
Western civilizations as a way of developing
Siam. Thus, he signed treaties with England,
France, Holland and Persia and expanded trade
between Siam and India, Indonesia, China and
Japan. These initiatives led to a proliferation of
international trade, and cemented ―... Ayutthaya‘s
reputation as an ‗emporium of the East‘ ...‖ at
this time, which rested largely ―... upon her role
as a focus for the trans-shipment of goods be-
tween Europe/India and China/Japan ...‖ (Stern-
stein, 1965: 108). Because of his enlightened
policies we could regard King Narai as
... a strange but also positive anachronism—or
precursor—for the Siam of the time. Not only
[because of] his wide spirit of religious tolerance
but also his positive interest in faraway lands,
their customs, religions and peoples ... (Sioris,
1992: 60).
In 1675 a Greek adventurer named Constan-
tine Phaulkon (1647–1688; Figure 3; Sioris, 1988)
came to Siam. He quickly learnt Thai, and being
fluent already in English, French, Portuguese
and Malay joined King Narai‘s court as a trans-
lator. Thanks to his prior experience with Eng-
land‘s East India Company he quickly emerged
as one of the King‘s favourites and gained in-
creasing power until he became the King‘s
principal advisor. As Sioris (1992: 60) remarks,
The adventurer, the old seaman, the man of
profit, changed into the mature and exper-
ienced courtier and politician, the intriguer—
and the trusted Counselor. Mere survival in
the exotic land had been secured. Now, the
investment in work and effort had to bring in
dividends of influence and power. At this junc-
ture there emerges the new Phaulkon, who
projects himself onto the great diplomatic chess-
board of the times, corresponding with popes,
monarchs, bishops, generals, politicians, in-
triguing with Jesuits, missionaries and diplo-
mats, planning or destroying great alliances,
undercutting or supporting old and new relig-
ions. The small shipboy of remote Cephallonia
was now wearing exotic golden uniforms and
receiving ambassadors and envoys ...
Through Phaulkon‘s influence, Siam forged
close diplomatic relations with the court of Louis
XIV of France (1638–1715) as part of a care-
fully-planned strategy to use the French as a
counter to the growing economic dominance of
the Dutch in Siam (see Cruysse, 2002; Hutch-
inson, 1933). King Narai also had heard of King
Louis XIV‘s military success over the Dutch dur-
ing the war of 1672–1679 (Love, 1994a). Mean-
while, for their part, the French
... had been seeking ways to establish France
as a great commercial, political and military

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 27
power in the Far East, in direct challenge to
Dutch hegemony. (Love, 1994b: 156).
Consequently, they were eager to establish a
major trading centre in Siam, and also to convert
the local population to Catholicism, so increas-
ing numbers of French missionaries and lay per-
sons made their way to Siam, and particularly
Ayutthaya, Lop Buri and Bangkok. Among their
number were architects, engineers and crafts-
men who became involved in the construction of
forts, and when King Narai decided to develop
Lop Buri as an alternative capital (Thavornthan-
asan, 1986) they helped design and build a new
palace, drains, fountains and a water reservoir.
In January 1684 two Thai ambassadors,
Pichai Warit and Pichit Maitri, accompanied by
a French missionary, Father Bénigne Vachet
(1641–1720) from la Société des Missions Étran-
gères de Paris who had been in Siam since
1671, went to France and had an audience with
King Louis. They presented the King with a letter
from King Narai inviting him to send astronomers
to Siam. The following year the French obliged,
and on 3 March 1685 a mission led by Chevalier
de Chaumont (1640–1710) sailed from Brest on
the l’Oiseau and la Maligne bound for Siam.
Accompanying de Chaumont were Father Vach-
et, François-Timoléone Choisy (1644–1724) and
a number of Jesuit astronomers. They arrived in
Siam on 24 September 1685 and were greeted
by two mandarins and an impressive retinue of
forty men, sent by King Narai. Meanwhile, the
King‘s astrologers had been assembled to deter-
mine ―... the luckiest day of the Year to be pitch-
ed upon for his [de Chaumont‘s official] Recep-
tion ...‖ at court (Love, 1994a: 60). This turned
out to be 18 October, when the French delegation
had an audience with King Narai (Figure 4) in
Ayutthaya.
According to de Chaumont (1686), at this time
His Majesty the King Narai is about 55 years
old, handsome, lovely, dark, has good behav-
ior, and is brave. He is also intelligent, a good
ruler … [and is] kindhearted …
Regrettably, there are no other descriptions of
King Narai, so we cannot ascertain whether the
likeness shown in Figure 1 is realistic or not.
What we do know, however, is that King Narai‘s
clothing shown in this representation is distinctly
non-Siamese: apparently, prior to meeting the
French he had entertained a Persian delegation,
and he liked their attire so much that he decided
to adopt it for his own court appearances (Smith-
ies and Bressen, 2001).
Soon afterwards the delegation proceeded to
Lop Buri (or Louvo as it was usually referred to
by the French).1 The city they encountered upon
their arrival was impressive, and was described
by Gervaise (1689) as ―… a town which is, so to
speak, in the Kingdom of Siam what Versailles
is in France.‖ Because King Narai favoured Lop
Figure 3: A contemporary drawing of Constantine Phaulkon
(en.wikipedia.org).
Figure 4: A painting showing Chevalier de Chaumont
presenting a letter from King Louis XIV to King Narai in 1685.
He is accompanied by the Jesuit missionaries, Fathers
Tachard and Vachet. Constantine Phaulkon is crouching on
the left, with his hand raised (en.wikipedia.com).

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 28
Buri over the official capital, Ayutthaya, he ―...
had caused to be carried out many works in his
desire to improve and embellish the town.‖ (Gib-
lin, 1904: 9). Thus, he repaired the ruined Bhud-
dhist temples, built a new palace and other
buildings, and surrounded them with attractive
gardens, ornamental fountains and water feat-
ures (e.g. see Chaumont, 1686; Gervaise, 1689;
Smith, 1880). Is it any surprise, then, that King
Narai liked to spend up to nine months of each
year in Lop Buri, enjoying the more relaxed
lifestyle, and
... pleasure trips to the forests abounding with
every variety of trees and to the wild mountain
scenery abounding in birds and beasts, and
[he] was enchanted with the romantic scenery
of the region. (Smith, 1880).
It was within this idyllic environment that the
French attended to affairs of state, ceremonies
and conferences (Giblin, 1904). Then on 10
December de Chaumont and Phaulkon signed an
agreement that gave French missionaries spec-
ial privileges in Siam, and as we shall see,
through the Jesuits this would soon benefit Sia-
mese astronomy. It is interesting that one of the
five conditions in the agreement specifically re-
flected King Narai‘s personal interest in science,
and especially in astronomy:
The King of Siam permits the Apostolic Mis-
sionaries to instruct any of his natural-born
subjects in any of the sciences, and to receive
them into any of their monasteries, schools,
and dwellings with similar privileges to those
enjoyed in the other monasteries of Siam, and
without constraint from anyone. The said mis-
sionaries are allowed to teach science, law,
and any other subjects that are compatible with
the Government and Laws of the realm. (Hutch-
inson, 1935: 221; our italics).
To understand King Narai‘s interest in astron-
omy and the reason for the inclusion of ast-
ronomers in the 1685 mission we need to ex-
amine his education. In keeping with his royal
pedigree, as a prince Narai received a sound
Buddhist temple education from the monks, but
he also was taught non-religious subjects such
as astrology, astronomy, mathematics and med-
icine by lay teachers. The young prince showed
a special interest in astronomy and astrology,
and it is noteworthy that his lay teacher in these
subjects later was appointed Siam‘s Chief Royal
Astrologer. Hodges (1999: 36) also reminds us
that
Narai‘s contact with foreigners also contributed
to his education. His reign coincided with Euro-
pean advances in the sciences associated with
navigation, astronomy and horology. He lived
in an age when humans were first beginning to
grasp the nature and extent of the cosmos ...
Once he was King, Narai was in an ideal
position to indulge his astronomical interests,
and he learnt about telescopes and other scien-
tific instruments, the newly-constructed Paris
Observatory and Jesuit astronomical activities in
Peking from Jesuits and others who were on
their way to Peking or returning home to Europe
and stopped off in Siam along the way. More-
over, he sometimes was able to influence the
types of gifts he received from visiting dignitar-
ies, which went far beyond the typical ―... cloth,
spices and jewellery of his predecessors ...‖ and
—at his specific request—included telescopes,
clocks and military equipment (ibid.). Thus,
among the gifts brought out to Siam by the 1685
delegation were a celestial globe, a terrestrial
globe, telescopes and other scientific instruments
(Tachard, 1686).
3 SIAM’S FIRST EUROPEAN
ASTRONOMERS
3.1 Father Antoine Thomas
Following King Narai‘s enlightened policy of pro-
moting increasing contact with Eastern and
Western nations, both Lop Buri and Ayutthaya
quickly acquired a cosmopolitan flavour with Ar-
menian, Chinese, Dutch, English, French, Ind-
ian, Japanese, Javanese, Malay, Persian, Portu-
guese and Turkish communities. Many of these
people worked for the state or had their own bus-
inesses, but there was always a transient pop-
ulation of visiting Europeans, Arabs, Indians and
Asians. Because of this, there is a wealth of
published material on seventeenth century Siam,
as book after book appeared describing—and
often singing the praises of—Ayutthaya and Lop
Buri. It must be remembered that by interna-
tional standards both were large cosmopolitan
cities.
Among the Europeans who settled in Ayu-
tthaya at this time were French missionaries
from the Société des Mission Étrangères de
Paris. The Société was formed to
... bypass the old privileges of the Portuguese
and Spanish missions that depended entirely
on the kings of Portugal and Spain, and to
launch a new missionary instrument at the
Pope‘s beck and call. (Cruysse, 1992: 64).
Their missionaries first arrived in Siam in 1662
(see Love, 1999), but they found that other Cath-
olic missionaries were already living in the city,
and thus began an intriguing and complicated
power-play involving different factions of Catho-
lics and different nationalities. To explain this
situation we need to understand that there were
different orders of the Roman Catholic faith (e.g.
Jesuits, Dominicans, Franciscans, etc.) and at
the time there was competition between the
Pope (the international leader of the Catholic
Church, and based in the Vatican) and the Kings
of Spain and Portugal (working collectively) for
control of Catholic missionaries world-wide. Un-
til the second half of the seventeenth century
All the Catholic missions in the East [i.e. in
Asia] were under Portuguese protection and
the personnel were composed mainly of Port-
uguese and Spaniards. (Hutchinson, 1933: 6;
his italics).

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 29
Then, from the 1660s,
... two rival Catholic missionary circuits shared
the Asian scene ... They engaged in a fierce
struggle where all kinds of dirty tricks were
allowed. It will surprise nobody that the Siam-
ese were sick and tired of the neverending
quarrels, and that very few among them felt
the urge to join the Church which preached
peace and brotherly love, but whose represent-
atives were at each other‘s throats. (Cruysse,
1992: 64–65).
Of all the Catholic faiths, the Jesuits had a
special passion for science, and especially math-
ematics and astronomy, and during the sixteen-
th century the Spaniard Jesuit, Francis Xavier,
founded missions in Asia. Then during the early
years of the seventeenth century
... his followers spread over the Indo-Chinese
Peninsula, and, when P‘ra Narai came to the
throne of Siam [in 1656] there were Jesuits as
well as Dominicans [already] established in
the Portuguese colony at Ayŭt‘ĭa. (Hutchinson,
1933: 6).
It was against this politico-religious backdrop
that Father Antoine Thomas (1644–1709), a Bel-
gian Jesuit missionary, arrived in Ayutthaya in
1681, and as far as we have been able to de-
termine he was the first European to carry out
serious astronomical observations and therefore
expose Siam to Western astronomy.
So who was this pioneer of scientific astron-
omy in Thailand? Antoine Thomas was born on
25 January 1644 in Namur, in what is now Bel-
gium. He joined the Jesuit Order in 1660, and
by 1678 had been ordained a priest. While
training for the priesthood he led a peripatetic
existence, between 1662 and 1675 studying in
Namur, Douai, Lille, Namur (again), Huy and
once again in Douai (in that order—see Collani,
n.d.). He taught at schools in Armentières, Huy
and Tournai,2 and served as a Professor of Phil-
osophy at the College de Marchiennes in Douai.
In the course of his training, Father Thomas
developed a passion for mathematics and astron-
omy, and between March 1678 and January 1680
he studied mathematics in Coimbra, Portugal.
Whilst there he observed a lunar eclipse, and he
published a short account of this in the Journal
des Sçavans (Thomas, 1679), the earliest Euro-
pean academic journal, which included obituaries
of notable people, church history, legal notes and,
of course, astronomy.
Thomas‘ goal was to carry out missionary
work in Japan, which ultimately would prove to
be impossible, but while trying to arrange this he
was forced to spend nearly a year in Siam,
arriving in Ayutthaya on 30 August 1681 (Col-
lani, n.d.). He was living there when the Feb-
ruary 1682 eclipse occurred.3
After finally realising that his dream of carry-
ing out missionary work in Japan was not to be,
Father Thomas determined to go to China in-
stead, and on 4 July 1682 he arrived in Macau.
He would spend the rest of his life living in China,
where he enjoyed a distinguished career in
astronomy and mathematics (Han, 2003; Jami,
2007; Witek, 2003). He died in Peking on 28
July 1709 at the age of 65 (Collani, n.d.).
Soon after arriving in Ayutthaya Father Thom-
as carried out solar observations in order to
determine the latitude of the city. This occurred
on 14 October 1681 and he conducted further
observations on 30 December 1681. When var-
ious corrections were applied, these gave val-
ues of 14° 18′ 21″ and 14° 20′ 18″ N respective-
ly (Thomas, 1692).4 Father Thomas indicates
that his observations were made from ―… the
House of the Society of Jesus in the suburbs, to
the south of Juthia [i.e. Ayutthaya].‖ (ibid.; our
English translation). This residence must have
been close to the Jesuit church in the Portu-
guese residential sector of Ayutthaya, which in
Figure 5 is marked by the ‗I‘ at the centre bottom
of the map, beside the western bank of the river.
This location is confirmed by a second—albeit
somewhat cruder—map of Ayutthaya, which was
published in 1686, and is reproduced here in Fig-
ure 6. The datum point for these latitude observa-
tions was a wooden board that was mounted high
on one of the walls of the church, and contained
an indented metal plate that was aligned parallel
to the horizon (ibid.).
There is no record of the precise location of
the Jesuit residence near the church (where
Father Thomas was based), but from Loubère‘s
(1693) account we can anticipate that it was
built of brick and was only one storey high:
The Europeans ... build with brick, every one
according to his Genius ... At the side of their
Houses, to keep off the Sun and not hinder the
Air, some do add Penthouses, which are some-
times supported by Pillars ... The Chambers [in
the main house] are large and full of windows,
to be the more fresh and airy ... (cited in Stern-
stein, 1965: 100).
While he was Belgian by birth, it is natural
that Father Thomas ended up living in the Portu-
guese sector of Ayutthaya given that there was
no suburb reserved for Belgians. During his re-
ligious training he spent some time in Portugal;
he came to Siam via Goa, the Portuguese col-
ony on the west coast of India; and when trying
to arrange to conduct missionary work in Japan
it was Portuguese supporters who lobbied (un-
successfully in the end) on his behalf (see Col-
lani, n.d.). All of his associations were with the
Portuguese, and it is noteworthy that
... Portuguese was the lingua franca for com-
munication with Europeans in Ayutthaya in the
seventeenth century ... (Smithies, 1989: 60).
3.2 The First Contingent of Astronomers
With Father Thomas‘ departure for China in July
1682, Siam lost its sole active European astron-
omer, but he was soon to be replaced, for the
1685 French delegation included

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 30
Figure 5: A map of Ayutthaya in the 1680s showing the location of the Portuguese residential precinct (marked ‗Portugals‘ to the
south of the river on the left, and above the Malayan precinct (after Loubère, 1693).
Figure 6: A map of Ayutthaya by Jean de Courtaulin de Maguellon (1686) confirms the location of the Jesuit church in the
Portuguese residential precinct. The inset map at top right shows Lop Buri (http://www.esnips.com/web/NDMI-Oldmap).

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 31
Table 2: Jesuit missionary-astronomers who came to Siam in 1685 with the French delegation.5
Name
Birth/Death Dates
Immediate Destination after Siam
Jean de Fontenay
1643–1710
China (1688–1702)
Joachim Bouvet
1656–1730
China (1688–1697; 1699 –1730)
Louis le Comte
1655–1728
China (1688–691)
Jean-François Gerbillon
1654–1707
China (1688–1707)
Guy Tachard
1648–1712
Remained in Siam
Claude de Visdelou
1656–1737
China (1688–1709); India (1709–1737)
... six Jesuit mathematicians [cum astrono-
mers] sent out by Louis XIV., under a royal
patent, to carry out scientific work in the Indies
and in China, in order, as the patent puts it, ―to
establish Security in Navigation and to improve
Sciences and Arts.‖ (Giblin, 1909: 1).
They were led by Father Jean de Fontenay (see
Table 2), and although they were supposed to
continue on to China, all but one of their number
would remain in Siam until the end of 1687 and
then move to Peking. The exception was Guy
Tachard (1651–1712; Figure 7), who would stay
behind and play a key political role in the devel-
opment of scientific astronomy in Siam (see
Orchiston et al., 2016b).
Before they left France, Tachard and the other
five Jesuit astronomers were admitted to the
Académie Royale des Sciences, and supplied
with astronomical instruments on the understand-
ing that these would be used—among other
things—to determine the latitude and longitude
of different geographical features and popula-
tion centres. Such data would later prove inval-
uable when creating maps of the Asian region.
As well as scientific instruments, the astrono-
mers were supplied with tables of Jovian satel-
lite phenomena, courtesy of Paris Observatory,
and various reference books and charts. And in
addition to astronomy, they also were requir-
ed to collect information on natural history, geo-
graphy, culture, etc.
Once in Siam the French Jesuit astronomers
unwittingly became involved in a power struggle
with non-Jesuit Catholic missionaries from the
Société des Mission Étrangères de Paris (Cruys-
se, 2002, Hutchinson, 1933). When the Jesuit
astronomers arrived, missionaries from the Soci-
été were already well established in Siam, and
their goal was simply to capture the minds,
hearts and souls of the Siamese by gathering as
many Catholic converts as possible. Whilst this
was an aim of the Jesuits, they also had scientif-
ic objectives in mind. To access King Narai both
parties had to use Constantine Phaulkon as an
intermediary, and most of those from the Société
despised him, whereas the Jesuits found him
helpful and supportive, partly because he was a
Jesuit convert himself and partly because of the
King‘s personal interest in astronomy. The Jes-
uits openly exploited this situation, and upon
arriving in Ayutthaya Tachard
... set himself to cultivate an intimacy with
Phaulkon acting as his secretary and confidant
... [and soon] was working on behalf of the
Jesuits to supplant Bishop Laneau [from the
Société des Mission Étrangères de Paris] as
intermediary between the French and Siamese
Courts. (Hutchinson, 1933: 25).
This tactic worked admirably, and Father Tach-
ard soon became King Narai‘s personal astro-
nomical consultant and eventually his scientific
ambassador, first to Paris and later to the Vatican
(Smithies and Bressen, 2001).
While Tachard could be viewed as an astro-
politician par excellence, others have painted a
less than charitable picture of him in a non-
astronomical context. For example, when back
in France with Chaumont and Choisy in 1686,
he usurped the rightful role of the three official
Siamese ambassadors and carried out secret
negotiations with the French court, and
Figure 7: A drawing of Father Guy
Tachard by Carlo Maratta (en.
wikipedia.org).
During the second French embassy in 1687 of
La Loubere and Ceberet, Tachard behaved
outrageously towards the accredited French
envoys ... Power had simply gone to his head.
He was as arrogant towards them as he was
subservient to Phaulkon. (Smithies, 1994: 176).
Smithies (ibid.) also states that Tachard ―... was
universally loathed by all who came into contact
with ...‖ (ibid.) him except for François Martin, and
he then assembles first-hand or second-hand
opinions of Capuchin Fathers from the Coraman-
del Coast, the Cardinale de Tournon, Chaille,
Choisy, employees of the French East India Com-
pany, Forbin, the Papal Legate in the Indies, the
Patriarch of Antioch and Vachet, to the effect
that Tachard was ―... imbued with foolhardiness

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 32
Table 3: Details of the 22 February 1682 lunar eclipse.
Totality
Local
Time
Moon
Altitude Azimuth
Sun
Altitude Azimuth
Start
05h 25m
+17° 267°
–19° 96°
Middle
06h 13m
+06° 279°
–07° 99°
End
07h 01m
–05° 282°
+05° 102°
to a degree beyond which it would not be pos-
sible to proceed ...‖; was ―... a swindler and an
impostor ...‖; and was ―... the most despicable
and pernicious of all men.‖ (Smithies, 1994:
177). Fellow professor, Dirk van der Cruysse
(1992: 67), also has little time for Tachard:
[He] ... was about to play a pernicious part in
Siamese-French relations, [and] is the leading
―bad character‖ in our story.
But are all of these criticisms justified? As we
have seen, there was no love lost between the
Jesuits and other factions within the Roman
Catholic Church or between the French Jesuits
in Siam and their confrères from the Société des
Mission Étrangères de Paris, and it is noteworthy
that all—or almost all—of Tachard‘s critics were
non-Jesuits. Undoubtedly Tachard had some
faults, but he was not all bad. Yet Vongsura-
vatana (1992) goes too far in trying to rehabili-
tate Tachard, and claim that he was ―... an extra-
ordinary diplomat who deserves a place of choice
in French maritime history ... [and] also deserves
to be considered a great diplomat by the Siam-
ese ...‖ (Vongsuravatana, 1994: 98).
4 LUNAR ECLIPSE OBSERVATIONS
Although there was interest during the seven-
teenth century in explaining the visibility of the
Moon prior to totality, astronomers mainly want-
ed to time lunar eclipses in order to determine
the longitudes of their observing sities. Link
(1959: 10) notes that
In the 17th and partly also in the 18th century
Hipparchos‘s old method for the determination
of longitudes was renovated using the tran-
sits of craters on the edge of the shadow ...
Though the accuracy of this method could not
exceed more than some tenth of a minute of
time, its utility was great in those times. For
instance the eclipse of 1634 observed in Cairo,
Aleppo and the western part of Europe, enabl-
ed the astronomers to shorten the Mediterran-
ean Sea by 1000 km in respect to its assumed
length before that time ...
In seventeenth Siam, lunar eclipses therefore
held special appeal. In the years immediately
following Father Thomas‘ arrival in Ayutthaya,
lunar eclipses were successfully observed on 22
Table 4: Details of the 11 December 1685 lunar eclipse.
Totality
Local
Time
Moon
Altitude Azimuith
Sun
Altitude Azimuth
Start
04h 37m
+26° 288°
–27° 109°
Middle
05h 29m
+15° 290°
–15° 110°
End
06h 21m
+03° 293°
–04° 113°
February 1682, 11 December 1685, 30 Novem-
ber 1686 and 15–16 April 1688 (Bhumadhon,
2000). The first two eclipses were associated
with the birth and early development of scientific
astronomy in Siam, and are discussed below.
4.1 The Eclipse of 22 February 1682
There is embarrassingly little information avail-
able, other than that Father Thomas (1692) suc-
cessfully observed this eclipse from Ayutthaya,6
and derived a longitude of 121° E of El Hierro for
the city (Tachard, 1686). The currently-accepted
value is 100° 33′ 54″ east of Greenwich, but note
that at this time the French measured longitude
from the island of El Hierro, which was 20° 23′
09″ west of Paris, and Paris is 2° 20′ 14″ east of
Greenwich.
Father Thomas probably observed the eclipse
from the Jesuit church, in the Portuguese district,
or just possibly from the veranda or courtyard of
the Jesuit residence near the church. From our
knowledge of the Moon‘s position at the time we
can ascertain that the eclipse would have been
visible from throughout this residential area of
Ayutthaya, as adjacent buildings would not have
impeded visual access to the western sky.
Listed in Table 3 are start, middle and end
times of the total phase of the lunar eclipse in
local time,7 along with the positions of the Moon
and Sun, as observed from Ayutthaya. We can
see that this eclipse was visible in the morning
shortly before the beginning of astronomical twi-
light, with the Moon located low in the western
sky. The Sun rose at 06h 39m local time, be-
fore the completion of the eclipse, so only the
very early parts of totality would have been
viewed in a completely dark sky. Mid-totality
took place just before the beginning of civil
twilight, so by this time the sky would have had
an obvious blue hue, and only the brighter stars
would still have been visible.
The eclipse was readily visible to the nak-
ed eye, and there is no mention that Father
Thomas used a telescope to record it, but in
order to record the times of the contacts and
derive a longitude for Ayutthaya from the obser-
vations he used a pendulum clock (Thomas,
1692).
4.2 The Eclipse of 11 December 1685
After arriving in Ayutthaya with Chevalier de
Chaumont‘s diplomatic mission, Father Fonte-
noy and his fellow Jesuits discovered that they
could not immediately continue on to China and
would have to remain in Siam for some time. At
first they were frustrated because they could not
use their astronomical instruments:
... because all the time we were at Ayutia the
City and the Camping places were so inundat-
ed that we had no place to set them up. The
very house where we were lodged, being of
wood, the least movement shook it so much

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 33
that our·Clocks and our Quadrants were disturb-
ed. (Tachard, 1686).8
This situation changed when they moved to Lop
Buri in order to prepare for a total lunar eclipse
that conveniently would occur on the night of
10–11 December 1685, during their stay in Siam.
Table 4 lists the start, middle and end times of
the total phase of this lunar eclipse in local time
based upon modern calculations, along with the
positions of the Moon and Sun, as observed from
Lop Buri. This eclipse was visible in the morn-
ing on 11 December 1685, with the start of tota-
lity occurring well before the beginning of astro-
nomical twilight. At this time, the Moon was low
in the sky about 20° north of due west. At mid-
totality, astronomical twilight had just begun,
and in the east there would have been a minor
twilight glow on the horizon 20° south of east.
On 22 November 1985 the French astron-
omers had a meeting with King Narai in Lop
Buri, and he honoured them by inviting them to
join him in observing the eclipse from his ‗country
retreat‘, ―... a very roomy Palace ... surrounded
by brick walls fairly high.‖ (Giblin, 1904: 11), locat-
ed at the water reservoir called ‗Tale Chup-
sawn‘ about 4 km east of Lop Buri (Giblin, 1904:
22). This small artificial lake is described by
Father Tachard in his 1686 book:
There is a large stretch of water which makes
of it a peninsula [where King Narai‘s ‗country
retreat‘ was located], and on this water the
King of Siam has built two frigates with six
small pieces of cannon, on which this Prince
takes pleasure in going about. Beyond this
canal [lake] is a forest, 15–20 leagues in ex-
tent and full of Elephants, Rhinoceros, Tigers,
Deer and Gazelles. (Giblin, 1904: 12).
The reservoir had been completed not long be-
fore in order to provide a continuing supply of
fresh water to the palace in Lop Buri. Armed
with three Galilean telescopes (these included a
12-ft and a 5-ft) and a clock, Phaulkon and the
astronomers visited the observing site on 9 De-
cember, and the French were suitably impress-
ed:
A more convenient spot could not be selected.
We saw the Heavens on all sides and we had
all the space necessary for setting up our
instruments. Having settled everything we re-
turned to Louvo. (Tachard, 1686).
Subsequently,
… we had cause to be transported to the Tale-
Poussonne our telescopes and a spring clock
very trustworthy and regulated by the Sun …
[so that we could] observe there the Eclipse,
according to the orders of the King. (ibid.).
Upon arrival, they immediately set up their in-
struments on the waterside terrace adjacent to
the reservoir, then they rested for 3–4 hours
before rising and heading for the observing site.
By this time ―It was then nearly three hours after
mid-night.‖ (ibid.).
Fortunately the night of 10–11 December was
clear (it was the dry season), and
We prepared for the King a very long telescope
of 5 feet [length] in a window of a saloon which
opened on the corridor [terrace] in which we
were.9 The Penumbra being well advanced
the King was informed and came at once to
the window. We were seated on Persian mats,
some with telescopes, others with the clock,
others ready to write the time of the obser-
vation. We saluted His Majesty with a pro-
found bow, after which the observations were
begun. (ibid.).
It is interesting that during the eclipse King Narai
… wished to look through a telescope 12 feet
long, which Father de Fontenay was using,
and we immediately carried it to him. He allow-
ed us to rise and stand up in his presence, and
he was quite willing to look through the Tele-
scope after we had done so, for it was neces-
sary to put it in position to show it to him.
Those who know the respectful attitude
which Siamese Kings expect from those who
may be in their presence have spoken to us of
this favour as of something very unique. (ibid.).
Figure 8 shows the Jesuit astronomers and King
Narai observing the eclipse, in the presence of
the prostrated court astrologers.10 From all ac-
counts, the King thoroughly enjoyed the experi-
ence, and
… expressed a special satisfaction seeing all
the spots [craters, etc.] of the Moon in the Tele-
scope, and in seeing that the plan [map] which
had been drawn of it at the Paris Observatory
agreed with it so well. He put several quest-
ions to us during the Eclipse. For example:
Why the Moon appeared upside down in the
Telescope? Why one could still see the part of
the Moon which was eclipsed? What time was
it at Paris? What could be the utility of such
observations made at the same time at two
places at such a distance apart? &c. (ibid.).
The map of the Moon referred to in this quota-
tion was one that Jean Dominique Cassini, the
Director of Paris Observatory, first presented to
the Academy of Sciences in Paris on 18 Febru-
ary 1679 (see Launay, 2003). It is reproduced
here as Figure 9,11 and clearly shows the maria,
highland regions and various distinctive craters
that would have attracted King Narai‘s attention.
It is interesting that Tachard (ibid.) also in-
cludes the times of the start and end of totality
that were recorded by the Jesuit astronomers.
These were 04h 23m and 06h 10m, both of which
are earlier than the times listed in Table 4 by 14
minutes and 11 minutes respectively. Using their
recorded times of totality the French computed
the longitude of Lop Buri to be 121° 02′ E of the
island of El Hierro. Meanwhile, the latitude of
Lop Buri later was reported to be 14° 48′ 17″ N
(Tachard, 1689). The currently-accepted value
is 14° 48′ 00″ N, while Lop Buri is now known to
be 118° 42′ E of the island of El Hierro.
The various quotations reproduced above
demonstrate that Father Tachard provided a de-
tailed account of this eclipse in his 1686 book

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 34
Figure 8: A drawing showing King Narai and the Jesuit astronomers observing the 11 December 1685 total lunar eclipse from the
King‘s country retreat which was on an island in the water reservoir that was located to the northeast of his palace in Lop B uri
(en.wikipedia.com).
Voyage de Siam des Pères Jésuites Envoyés par
Roi aux Indes & à la Chine. Choisy (1687) also
mentions the eclipse in his book, but he supplies
no details, and does not even identify the water
reservoir—as opposed to King Narai‘s palace in
Lop Buri—as the site where the observations
took place.
As we have seen, in addition to Tachard‘s
detailed description of the eclipse observations
there is the drawing shown here in Figure 8,
which was included in Tachard‘s 1686 book. But
how reliable is this drawing as a realistic depic-
tion of the country retreat, King Narai and the
astronomers and their instruments, and their ob-
servations of the eclipse?
All six Jesuit astronomers are shown in the
drawing, along with King Narai, his advisor, Con-
stantine Phaulkon (in the pavilion with the King),
and six court astrologers (who, incidentally, are
never mentioned in the contemporary European
accounts of this eclipse). Three different tele-
scopes are shown in the drawing if we assume
that the Jesuit astronomer closest to the King‘s
pavilion is holding a telescope support and not a
fourth telescope, and this tallies with the account
that during the eclipse some of the astronomers
used telescopes, others attended the clock and
yet others recorded the observations. Two of the
telescopes were stated to be 5-ft and 12-ft in
length and the size of the third telescope is not
mentioned, yet in Figure 8 the telescope used
by King Narai is only ~20% longer than the
lengths of the two telescopes used by the Jesuit
astronomers—which are similar in length—not
~240% longer (and this takes no account of per-
spective). From this observation alone we can
conclude that the drawing contains an element
of artistic licence.
Nor does the drawing in Figure 8 realistically
depict the lunar eclipse itself. Knowing the alt-
itude and azimuth of the Moon at the time of
totality and the fact that King Narai observed
through a window in his country retreat, we can
establish that the King and the Jesuit astrono-
mers had to be located on the western side of
the country retreat. The azimuth of the Moon
(~22°) is realistically depicted in the drawing (cf.
Table 4), but the Moon should not have been
included in the diagram at all for at the time it
was located in the northwestern sky whereas
only part of the sky extending from the northeast
to the southeast is shown. The Moon therefore

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 35
Figure 9: A copy of the 1679 map of the Moon produced at Paris Observatory that was consulted by King Narai and the French
astronomers during the 11 December 1685 eclipse (© Observatoire de Paris).
would have been located in the sky behind the
‗artist‘s position‘, as depicted in the drawing.
So, allowing for perspective, we can see that
King Narai has his telescope pointing in approx-
imately the correct direction, but the two tele-
scopes of the Jesuit astronomers are pointing in
quite the wrong direction.
The afore-mentioned comments reinforce the
view that the Figure 8 drawing cannot be accept-
ed as a realistic depiction of the eclipse obser-
vations. Is this confirmed by architectural and
other details that are shown in this drawing? For-
tunately, some of the walls of the water reserv-
oir country retreat have survived, and these show
clearly that the design of most of the windows
there mirrored those found in King Narai‘s pal-
ace in Lop Buri and in stately houses that were
constructed in Lop Buri at the time. As illu-
strated in Figure 10, most of the windows were
rectangular and with ‗portrait‘ orientations (as
opposed to the ‗landscape‘ orientation depicted
in Figure 8). Moreover, most of the windows at
the water reservoir country retreat had lintels
immediately above and below them, and there-
fore lacked the arched top shown in Figure 8.
Yet there are some exceptions (for example, the
building shown in Figure 11), but we can see
that although the general shape of each window
is identical, their proportions differ markedly from
King Narai‘s ‗viewing window‘ depicted in Figure
8.
In Figure 8, the rather pagoda-like form of the
roof above the pavilion in which King Narai is
located also is an artistic aberration. Contempor-

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 36
Figure 10: A view, looking north, of the ruins of King Narai‘s country retreat at the water reservoir site in Lop Buri. This photograph
was taken in October 2014 (photograph: Wayne Orchiston).
Figure 11: A close-up view of the building in the left foreground in Figure 10, which has windows with vaulted tops (photograph:
Wayne Orchiston).
orary accounts of the palaces and other royal
buildings erected during King Narai‘s reign indi-
cate that they contained one or a succession of
gable roofs, none of which stylistically reflected
seventeenth century Siamese Buddhist temple
architecture (e.g. see Sternstein, 1965).
Finally, we should note that the pennant
shown at top left in Figure 8 erroneously sug-
gests that the eclipse observations took place at
King Narai‘s palace in Lop Buri, and not at his
water reservoir country retreat near Lop Buri.
All of this additional evidence confirms that
we cannot accept the drawing in Figure 8 as a
realistic ‗photographic‘ depiction of the eclipse
observations, and this tallies with Michel Jacq-
Hergoualc‘h‘s evaluation. In 1986 he prepared an

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 37
Figure 12: The edge of the waterwide terrace along the western margin of the country retreat is indicated by the extended
foundations on the left side of this image (photograph: Wayne Orchiston).
exhibition at the Musée de l‘Orangerie in Paris
which included this drawing. In his exhibition cat-
alogue Jacq-Hergoualc‘h (1986) noted that this
figure and others in Tachard‘s 1686 tome were
drawn by Pierre-Paul Sevin and engraved in Paris
by Cornelius-Martin Vermeulen, even though nei-
ther was a member of the 1685 delegation to
Ayutthaya and Lop Buri, or had ever visited Siam!
Smithies (2003: 191–192) concludes that
The drawings and engravings were probably
made in great haste after a few casual descrip-
tions gleaned from the manuscript [of Tach-
ard‘s 1686 book] or possibly Tachard in person,
and perhaps sketches which he may or may
not have seen.
Notwithstanding these comments, and despite
the somewhat dilapidated state of the western
side of the country retreat (when compared to the
southern walls), we were able to correlate exist-
ing foundations with the covered walkway shown
in Figure 8, and these are shown in Figure 10
starting at the main building and leading diag-
onally across the photograph towards the bot-
tom right margin. This marks one wall of the
walkway and the other runs near the right-hand
wall of the ruined room on the left foreground in
this photograph. This covered walkway led from
the main building, and would have provided safe
and ready access to those rooms along the west-
ern side of the country retreat both day and night,
and in all kinds of weather.
We also were able to identify foundations
that marked the margin of the terrace that
fringed the western side of the country retreat
and directly abutted the water reservoir (as illu-
istrated in Figure 8). These foundations are
shown in Figure 12, and run continuously along
the full length of the country retreat.
In Figure 8 it is apparent that there is no
indication of the country retreat main building
behind the small single-storey room where King
Narai is conducting his observations, and if this
was intentional it would suggest that this room
was located either to the north or the south of
the main building and access to it was afforded
via the covered walkway.
If this is a valid interpretation and our ident-
ification of the foundations of the covered walk-
way and margin of the waterside terrace are
correct, then we can tentatively identify King
Narai‘s location when he observed the 11 De-
ember 1685 lunar eclipse. He was in the room,
now in ruins, shown in the left foreground in
Figure 10, in close-up in Figure 11 and on the
extreme right (and partly obscured) in Figure 12.
Figure 13 is a scale drawing showing the lo-
cation of this ‗pavilion‘ relative to the main build-
ings of the country retreat, the covered walkway
and the edge of the terrace beside the water
reservoir.
More than one hundred years ago, the
Australian-born Director of the Thai Royal Survey

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 38
Department, Ronald Worthy Giblin, examined
sites associated with King Narai and had no
trouble finding the water reservoir:
Making now a short excursion into the country,
less than a league [from King Narai‘s palace in
Lop Buri] will take us to the Tale Chupsawn,
the reservoir built by King Narai. Reference to
a map made up by sheets of the cadastral sur-
vey will show just how this small artificial lake
is situated with regard to the town. It must be
remembered that to the east the ground slopes
upwards to form a low range of hills running
north and south. These hills, with the somewhat
striking and jagged peaks of the hills near Pra-
bat, may be seen from the northern railway
line. The reservoir is enclosed by a heavy earth
embankment, nearly 4½ miles long. This bank
is about 12 to 13 feet high, and the area avail-
Figure 13: A plan showing the location of the pavilion from
which King Narai observed the eclipse (purple rectangle),
the edge of the waterside terrace (red dashed line), the
covered walkway (red dotted lines) and the main and other
adjacent country retreat buildings (green outline) (plan:
Wayne Orchiston).
able for the storage of water is roughly one
square mile. Mr. Irwin[12] ... is of opinion that
the probable depth of water, when the tank
was full, came to not less than nine feet and a
half, deeper in some places and less in others
...
Within the reservoir and near the west-
ern embankment on a small elevated piece of
ground stand the ruins of the King‘s country res-
idence. It was here he took part in the obser-
vation of an eclipse of the moon, recorded by
Father Tachard. (Giblin, 1904: 22; our italics).
This would have written not long before Giblin‘s
paper was published in 1904 in the Journal of
the Siam Society, and at that time the water
reservoir and King Narai‘s country retreat were
easily recognisable.
The cadastral maps that Giblin refers to in
the above quotation were prepared sometime
between 1895 and 1903, but enquiries in Bang-
kok revealed that unfortunately they are no long-
er extant (Visanu Euarchukiati, pers. comm, Nov-
ember 2015), and moreover, copies of them
could not be located in Bangkok (ibid.) or in Lop
Buri. So they can no longer be used to identify
the water reservoir and artificial island where the
country retreat was located ―... with regard to the
town [of Lop Buri].‖ However, aerial photographs
of the region (e.g. see Goggle maps) clearly
show the country retreat and the artificial island.
The latter is elliptical in shape, and measures
~55m N-S by ~45m E-W. A field reconnaisance
in November 2015 by the first two authors of this
paper revealed that despite the passage of time,
the boundaries of this island were obvious, with
the land sloping down steeply, especially to the
north, east and south. Aerial photographs also
revealed that the country retreat was not cen-
trally-located on the island, but was close to its
western edge. To the east of the main building
there is now an area of lawn, which back in 1685
would have contained attractive gardens, and
perhaps fountains, if the beautification of King
Narai‘s palace in Lop Buri is any indication.
Despite the absence of Mr Irwins‘ cadastral
maps, aerial photographs and a field reconnai-
sance (also made in November 2015) easily
allowed us to identify the almost 4.5-mile long
12–13 foot high heavy earth and stone embank-
ment that was built in the early 1680s to create
the reservoir. As Figure 14 indicates, modern
roads now run along the top of embankment, and
where recent construction work is absent it is
easy to see the land sloping down steeply from
these two roads to what originally was the floor
of the water reservoir. Meanwhile, it also is tel-
ling that although this historic water reservoir no
longer exists per se, there are still extensive
expanses of emponded water in this area (see
Figure 14), indicating the low-lying nature of the
land where the water reservoir once was and the
continuing effectiveness of the southern en-
bankment.
5 DISCUSSION
5.1 The 1682 and 1685 Eclipses: The Nature
of the Evidence
It is regrettable that so little information has been
published about the Jesuit observations that were
made in Siam of the February 1682 and Decem-
ber 1685 total lunar eclipses, and it remains to
be seen whether relevant archival records have
survived. However, in the paper where he pro-
vides English translations of selected contents of
Tachard‘s Voyage de Siam des Pères Jésuites
Envoyés par le Roi aux Indes & à la Chine
(1686), Giblin (1909: 14) has these sobering com-
ments:
The foregoing pages contain all that is to be
extracted from the two volumes of travels pub-
lished by Father Tachard. It must be admitted
that the results in quantity do not amount to

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 39
Figure 14: A map of part of Lop Buri showing the location of King Narai‘s water reservoir and ‗country retreat‘ in relation to his
palace. The red dots mark the position of the embankment that was erected to stop run-off from the mountains to the east and form
the water reservoir. Terracotta pipes carried the water from the southwestern corner of the embankment to King Narai‘s palace
(map modifications: Wayne Orchiston).
very much, but this would hardly be the right
way in which to weigh them. At the time when
the observations were made they furnished
values which were, no doubt, acceptable and
accepted as the best available for use for the
construction of charts and for navigation pur-
poses. From an historical point of view the fact
that the observations were taken at all, and the
circumstances surrounding them must always
remain of interest, especially to those connect-
ed with Siam and concerned in any way in its
past, whilst allied to this aspect of the case lies
the possibility or power, which has its utility to
a surveyor, to institute comparisons between
the results obtained then and those of a later
date.
5.2 Subsequent Seventeenth Century
Astronomical Developments in Siam
The successful observations of the lunar eclipse
of 11 December 1685 encouraged Phaulkon to
propose the establishment of a major observa-
tory at Lop Buri, and King Narai agreed to this.
The result was Wat San Paulo, an impressive
two-storey rectangular structure with a large in-
ternal courtyard, and a four-storey tower Obser-
vatory at one end (see Figure 15). The Ob-
servatory section of this large building, inspired
in part by the Paris Observatory, was completed
in 1687 and its design and inspiration are dis-
cussed in Orchiston et al. (2016b), along with an
account of the surviving remains of this historic
observatory building.
King Narai was so impressed by the achieve-
ments of the first contingent of French astrono-
mers that he invited King Louis XIV to send
more astronomers to Siam, and at the end of Sep-
tember 1687 a second contingent, totalling four-
teen Jesuit astronomers, arrived in Ayutthaya.13
For further details see Orchiston et al. (2016b).
Between 1686 and 1688 (inclusive) the French
astronomers used state-of-the-art telescopes
and other astronomical instruments to carry out
observations of a comet; two further total lunar
eclipses; Jovian satellite phenomena; conjunct-
tions of Mars; an occultation of Jupiter by the
Moon; and a new double star. The last serious
astronomical observations they carried out at
Lop Buri were of the partial solar eclipse of 30
April 1688 (see Orchiston et al., 2016a).
5.3 The Demise of Scientific Astronomy at
Lop Buri
The success of the French Jesuit astronomers
was in large part due to the patronage of King
Narai and the role that Constantine Phaulkon
played in fostering Siamese-French relations, but
this combination ultimately would lead to their
downfall (see Cruysse, 2002; Le Blanc, 1692;
Smithies, 2002). Not unexpectedly, Phaulkon‘s

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 40
Figure 15: A contemporary drawing of Wat San Paulo, with its distinctive 4-storey observatory (en.wikipedia.org).
rise to power in Siam generated envy among
some members of the Royal Family, including
Pra Phetracha, King Narai‘s foster brother. By
1688 King Narai was terminally ill (it is thought
by some that he was poisoned), and a malicious
rumour spread that Phaulkon wished to become
the next King of Siam and planned to install the
designated heir, Phra Pui, as a puppet ruler. Pra
Phetracha used this as an excuse to stage a
coup d’etat, and Phaulkon, Phra Pui and their
supporters were arrested and on 5 June 1688
they were executed.14 King Narai was mortified
when he learnt of this, but he was too weak to
organize a counter-offensive and died soon after-
wards, on 11 July 1688.
Pra Phetracha then went and installed himself
as the new King of Ayutthaya, and reversed King
Narai‘s previous enlightened policies by closing
Siam‘s ‗doors‘ to the West and expelling most
of the foreigners who were living there (Smith-
ies, 2002).15 This led to the immediate close-
down of Wat San Paulo. All but one of the Jes-
uit astronomers there quickly moved to the
protection of the French fort in Bangkok and
from there sailed for India, thus bringing to an
abrupt end an all-too-short, yet extremely pro-
ductive, period of scientific astronomical activity
in Siam. However, adopting a very different view-
point, Professor Dirk van der Cruysse (1992: 64)
concludes that
Whether one likes it or not, the story of the
commercial, religious and diplomatic contacts
between Louis XIV and Phra Narai is the story
of a failure.
Meanwhile, in his encyclopaedic A History of
Southeast Asia, the distinguished British histor-
ian, Professor D.G.E. Hall (1981: 397), points
out that
... the reaction against the policy of King Narai
and Constant Phaulkon had caused such a
powerful upsurge of anti-foreign sentiment that,
until the days of [King] Mongkut ... Siam was
to be very chary of granting privileges to Euro-
peans.
Thus, nearly two centuries passed before West-
ern astronomers were able to re-instate—albeit
temporarily—scientific astronomy in Siam, first in
1868 when French astronomers would observe
a total solar eclipse from Wa Ko (see Figure 2)
under the patronage of King Rama IV (Orchiston
and Soonthornthum, 2016), and then in 1875
when British astronomers would observe an-
other total solar eclipse, this time from near
Phetchaburi (see Figure 2) and with the support
of King Rama V (Hutawarakorn-Kramer and Kra-
mer, 2006). This Royal patronage of scientific
astronomy initiated by King Narai and demon-
strated by Kings Rama IV and V has continued
through to the present day, with strong support
from His Majesty King Bhumibol Adulyadej
(Rama IX) and Her Royal Highness Princess
Maha Chakri Sirindhorn (see Soonthornthum,
2011), culminating in the establishment of the
National Astronomical Research Institute of Thai-

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 41
Figure 16: The plaque at the water reservoir site; note the erroneous inclusion of the 1688 solar eclipse on the second and third
lines in the English-language text (photograph: Wayne Orchiston).
land in Chiang Mai in 2009 and the opening of
the Thai National Observatory and its 2.4-m
Ritchey-Chrétien telescope on Doi Inthanon (see
Figure 2) in 2013.
5.4 Promoting the Early History of Scientific
Astronomy in Siam
Since we do not know precisely where Father
Thomas was located within the Portuguese res-
idential sector when he observed the 1682 lunar
eclipse, it is understandable that no attempt has
been made to commemorate the site with a
plaque, and even attempts to pinpoint the exact
location of the Jesuit church have been unsuc-
cessful (see Vandenberg, 2010).
Fortunately, this is not so at Wat San Paulo16
or at the water reservoir, where commemorative
plaques and interpretive display panels have
been erected that alert visitors to the astronomi-
cal significance of both sites. However, it is to be
regretted that both the plaque (Figure 16) and
the panel at the water reservoir include a ser-
ious error: in addition to mentioning the 11 De-
cember 1685 total lunar eclipse, they state that
the 30 April 1688 partial solar eclipse also was
observed from this site. In fact, it was observed
from King Narai‘s palace in Lop Buri, as docu-
mented elsewhere (see Orchiston et al., 2016a).
Finally, we should note that King Narai‘s
liaison with the West in order to develop Siam
has not been neglected by those responsible for
promoting Thailand‘s history. Thus, within one
of the two large round-abouts on the highway
that leads into the centre of Lop Buri from the
east there is an imposing statue of this famous
king who facilitated the birth of scientific
astronomy in Siam (Figure 17).
6 CONCLUDING REMARKS
Largely because of King Narai‘s personal inter-
est in astronomy, and the influence of his main
councillor, Constantine Phaulkon, Siam (present-
day Thailand) experienced the first blossoming
of Western scientific astronomy in the seven-
teenth century. On 14 October 1681 the Belgian
Jesuit mathematician and astronomer Father An-
toine Thomas observed the Sun in order to de-
termine the latitude of Ayutthaya, and this is the
first scientific astronomical observation that is
known to have been made from Siam. Then, on
22 February 1682, he observed a total lunar
eclipse and determined the longitude of the city.
Later, on 11 December 1685, a contingent of six
French Jesuit astronomers joined King Narai
and observed a total lunar eclipse from the
King‘s country retreat near Lop Buri, using three
Galilean telescopes and a pendulum clock. For
reference purposes, they had access to the
latest Moon map from Paris Observatory.
The success of the latter observations in-
spired the construction of a large well-equipped
astronomical observatory at Lop Buri, and further
astronomical observations were made, both there
and at Ayutthaya, until 1688 when the European

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 42
astronomers were obliged to leave Siam follow-
ing King Narai‘s untimely death.
Nonetheless, for seven short years—between
1681 and 1688 (inclusive)—scientific astronomy
flourished in Siam, and the 1682 and 1685 lunar
eclipses played a very important role in these
developments.
7 NOTES
1. In the 1680s Lop Buri was variously referred
to as Louvo (Tachard, 1686), Louveau (Ger-
vaise, 1689), Luvo (see Giblin, 1904) and La-
wo (ibid.) by the French.
Figure 17: The King Narai monument at the roundabout in
Lop Buri (photograph: Wayne Orchiston).
2. In the mid- to late-seventeenth century the
political geography of Europe was quite dif-
ferent to that found there today (e.g. see
Wiesner, 2006). As already stated, Namur is
in present-day Belgium, as are Lille and Tour-
nai, while Armentières, Douai and Huy are in
France.
3. Constantine Phaulkon played a key role in
facilitating the development of scientific as-
tronomy in Siam, and it may be that initial-
ly he acquired this sympathy for astronomy
from Father Thomas, who on 2 May 1682
(Smithies, 1994: 176)—not long after the 22
February lunar eclipse—converted him from
the Church of England faith to Roman Cath-
olicism (Hutchinson, 1933).
4. The currently-accepted value for the latitude
of Ayutthaya is 14° 21′ 12″ N.
5. Professor Michael Smithies (2003: 189) is a
highly-respected authority on Siam of the
1680s, but he errs in stating that those listed
in Table 2 ―… as well as being mathematic-
ians were also astrologers …‖ Today the dis-
tinction between astrology and astronomy is
very obvious to everyone, so perhaps he was
misled by the English translation of Tach-
ard‘s 1686 volume, which reads: Relation of
the Voyage to Siam Performed by Six Jesuits
sent by the French King, to the Indies and
China, in the Year 1685, with their Astrolog-
ical Observations, and their Remarks on Nat-
ural Philosophy, Geography, Hydrography,
and History (Tachard, 1688). This is a clear
mistranslation, as the original volume refers
specifically to ‗Astronomical Observations‘
and does not mention astrology.
6. Bhumadhon (2000) gives the impression that
this eclipse was observed by Father Thomas
and Father Gouye from Ayutthaya, but the
original French account (Gouye, 1692: 693)
clearly identifies Thomas as the sole observ-
er. The confusion appears to have arisen be-
cause even though Gouye was tasked with
publishing the astronomical observations of
the Jesuit missionary-astronomers who were
based in Siam, he also liked to add his own
comments and corrections. However, Gouye‘s
biography (see Thomas Gouye, n.d.) clearly
indicates that he spent his whole life in France
and never visited Siam.
7. All of the times listed in Tables 3 and 4 were
calculated using Herald‘s OCCULT v3.6 and
the NASA Catalog, which agreed to within
one minute in all instances.
8. This quotation and subsequent ones listed as
‗Tachard (1686)‘ are actually taken directly
from Giblin (1909) and are Giblin‘s English
translations of the astronomical excerpts con-
tained in Tachard‘s 2-volume work Voyage
de Siam des Pères Jésuites Envoyés par le
Roi aux Indes & à la Chine (1686).
9. Even though the presents that King Louis XIV
gave King Narai included telescopes, it is
interesting that the Siamese king did not use
one of these to observe the lunar eclipse, re-
lying instead on a telescope supplied on the
night by the Jesuit astronomers.
10. Soonthornthum (2011) erroneously states
that this eclipse was observed from the yet-
to-be constructed Jesuit observatory at Wat
San Paulo, in Lop Buri itself, and not from
King Narai‘s country retreat.
11. The original map is in the Paris Observatory
Library and Archives and measures 550 ×
563 mm. The diameter of the Moon is 530
mm (Launay, 2003). Subsequently, this map
was engraved by Jean Patigny, and distribu-
ted to interested parties—including the Jesuit
astronomers who went to Siam.

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 43
12. Giblin (1904: 23) identifies Mr A.J. Irwin as
the individual who conducted the cadastral
survey of the district and mapped the water
reservoir. The Royal Thai Survey Department
was founded by King Rama V in 1886, and
the cadastral survey commenced ten years
later (Giblin, 2008).
13. .....Smithies (2003: 192) also refers to these
astronomers as astrologers.
14. This is sometimes referred to as the ‗1688
Siamese Revolution‘, even though it was not
a popular uprising, or a ‗revolution‘, in the
strict sense of the word.
15. Thus ended France‘s brief but economically-
successful escapade in Siam. The only con-
cession Pra Phetracha made to foreigners
was to allow the Dutch to maintain a single
factory in Siam (Love, 1994a).
16. However, there is confusion over the correct
spelling of Wat San Paulo, with both this
(correct) version and ‗Wat San Paolo‘ feat-
uring at different times on different interpret-
ive panels at the site itself! Soonthornthum
(2011: 181) also uses Wat San Paolo.
8 ACKNOWLEDGEMENTS
We are grateful to the following for their assist-
ance: Phuthorn Bhumadhon and Visanu Euar-
chukiati (Bangkok, Thailand); Dr Suzanne Débar-
bat and Emilie Kaftan (Paris Observatory); Rung-
sirit Ngamsirit, Ms Savitee Chainarong and Chit-
chai Praditduang (Lop Buri City Hall, Thailand);
Chalovy Mayanthong (Department of Fine Arts,
Kraisorm Siharat Pavilion, Lop Buri, Thailand) and
Pisit Nitiyanant (NARIT). We are very grateful to
the Paris Observatory for permission to publish
Figure 9. This research is based on data gather-
ered during a detailed literature survey and three
different visits to Lop Buri and Ayutthaya, in 2014
and 2015. We wish to thank NARIT for funding
the last of these field trips.
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Professor Wayne Orchiston works as a Senior Re-
searcher at the National Astronomical Research Inst-
itute of Thailand and is an Adjunct Professor of Astron-
omy at the University of Southern Queensland in
Toowoomba, Australia. He has published extensively
on historic transits of Venus
and solar eclipses; historic
telescopes and observator-
ies; the history of cometary
and asteroidal astronomy; the
history of meteoritics; and the
history of radio astronomy.
Since he joined NARIT, his
research interests increasing-
ly have focussed on Asia, and
especially Indian, Indonesian,
Japanese, Philippines and
Thai astronomy, and astronomical links between SE
Asia and India and SE Asia and Australia. Wayne has
been a member of the IAU since 1985, and has been
very active in commissions dealing with history of

W. & D.L. Orchiston, M. George and B .Soonthornthum The First Observations of Lunar Eclipses Made in Siam
Page 45
astronomy, radio astronomy, and education and
development. Currently he is the Vice-President of
Commission C3 (History of Astronomy). In 1998 he
co-founded the Journal of Astronomical History and
Heritage, and is the current Editor. In 2013 the IAU
named minor planet ‗48471 Orchiston‘ after him.
Mrs Darunee Lingling Orchiston is the owner and
manager of the B-N shop in
Chiang Mai, Thailand. She
enjoys learning about Thai
astronomical history, help-
ing her husband with his
studies and accompanying
him on research trips. Her
Thai language skills were
critical for the successful
completion of this research
project. She is very proud
of this research paper, which
is her first astronomy publication.
Martin George is the Collections and Research Man-
ager at the Queen Victoria Museum and Art Gallery in
Launceston, Tasmania, and
also is responsible for the
Museum‘s planetarium and
astronomy collections. He
also is a Research Associate
of the National Astronomical
Research Institute of Thai-
land in Chiang Mai, and is a
former President of the In-
ternational Planetarium So-
ciety. Martin has a special
research interest in the hist-
ory of radio astronomy, and is completing a part-time
Ph.D. on the development of low frequency radio
astronomy in Tasmania through the University of
Southern Queensland, supervised by Professors
Wayne Orchiston and Richard Wielebinski (and
originally also by Professor Bruce Slee). Martin is the
Administrator of the Grote Reber Medal for Radio
Astronomy, and is a member of the IAU Working
Group on Historic Radio Astronomy.
Professor Boonrucksar Soonthornthum is the Exec-
utive Director of the National Astronomical Research
Institute of Thailand and has D.Sc. degrees in physics
and in astrophysics. He has
research interests in astro-
physics (especially binary
stars), the history of Thai-
land astronomy, and astro-
nomical education, and he
has published on all of
these topics. He is a long-
standing member of the
IAU; is very actively involv-
ed in the Astronomy Olymp-
iad movement; and is the
founder and chairman of
the Southeast Asian Astronomy Network (SEAAN).
Boonrucksar has arranged many international confer-
ences, and research collaborations between NARIT
and over-seas institutions.