365daysDate: August 8, 2009

Title: A History of Modern Astronomy in Thailand Part 1


Podcaster: Visanu Euarchukiati

Organization: Khaikhan Nithan Dao

Description: Part 1 tells about Thailand’s astronomy before the 20th Century. Not long after the advent of the telescope, late 17th Century Siam (former name of Thailand) built the first modern astronomical observatory in the far east and began networking with Cassini’s Paris Observatory. Nearly 200 years later King Rama IV or King Mongkut, of the King and I story, was an accomplished astronomer. He accurately predicted the time and location of the total solar eclipse of August 18, 1868 to the acclaim of professional European astronomers. Finally, King Rama V gave his support to Sir Arthur Schuster’s Royal Society total solar eclipse expedition in 1875. Incidental music is taken from King Rama VII’s Ratri Pradap Dao (Starry night), performed by Thailand Philharmonic Orchestra, conducted by Gudni Emilsson.

Bio: Visanu Euarchukiati is an astronomy enthusiast working and living in Thailand. An active member of the Thai Astronomical Society, Visanu served as the Society’s executive committee and played a major role in the production of Thailand’s first English-Thai Dictionary of Astronomy. He also writes and translates astronomy articles for magazines and has a book of astronomy tidbits and anecdotes published under his name. His special interests in astronomy cover archeoastronomy and star tales. Visanu is the publisher of a podcasting website Khaikhan Nithan Dao (, telling star tales from all over the world in Thai language.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Paul Jarman and dedicated to Alasdair Murdoch, a friend no longer here.



Hello. My name is Visanu Euarchukiati. I’m an astronomy enthusiast living and working in Thailand.

Just in case you have never heard of my country, Thailand is a developing country in Southeast Asia formerly known as Siam. Yes, the Siam of the Siamese twins and Siamese cat. The name of the country was changed from Siam to Thailand in 1939.

I call my series of episodes for the 365 Days of Astronomy “A History of Modern Astronomy in Thailand.” Modern astronomy generally means the astronomy after Galileo had looked at the heavens. That is of course 400 years ago, which is why we are having the International Year of Astronomy this year.

You might think that, wow, 400 years ago, I’ve never heard of Thailand, let alone knowing how important it was in astronomy. And you’re right. Our indigenous astronomy—based on Indian astronomy—was, really, utilitarian, being used for astrology, agriculture, and to tell directions. But, still, we got involved from time to time.

Today’s episode is Part 1 of the history. It is for events that took place before the 20th Century. Anything after that will be in Part 2.

Ayutthaya – King Narai

So for Part 1 we start with the time of King Narai the Great of the Kingdom of Ayutthaya whose reign, from 1656 to 1688, coincided with that of King Louis XIV of France. After King Narai allowed the French Catholic mission to establish in Siam in 1662, a close diplomatic relationship between Siam and France ensued. There were a series of embassies from Siam to France and vice versa. The affairs were orchestrated by a Greek named Phaulkon, who served as the Siamese prime minister, and the Catholic church which tried to convert the King to Christianity.

The King did not convert, but he allowed the Catholics to disseminate Christianity in Ayutthaya, the capital city, and also in Lawo, the second capital at the time which today is called Lop Buri.

The Catholic priests in Ayutthaya built a small observatory where they made astronomical observations and reported their results back to Paris Observatory. An example is an observation of a total lunar eclipse in 1682 from Siam which was included in a compendium of observations of the same eclipse contributed by such big names as Hevelius, Flamsteed, Cassini, and Fontenay.

That last name was not so big, but was one of the six Jesuit priests who arrived in Siam in 1685. These priests accompanied King Narai during the observation of a lunar eclipse in December 11, 1685 in Lawo. A report of the event was also sent to Cassini in Paris. The King was impressed with the priests’ science and promised to build an observatory for them.

From 1687 onwards observation started at this new observatory. The true name of the new church and observatory complex is now lost, but the locals call the site Wat San Paolo. The allusion to Saint Paul hints that this could really be its original name, but we can never tell. There were observations of eclipses, Mars, Jupiter and its satellites, and southern constellations. The longitude triangulation using Jupiter’s Galilean satellites as suggested by Galileo was likely performed there as well. Observation reports from Wat San Paolo are still kept at Paris Observatory to this day.

On April 30, 1688, the Jesuits served the ailing King Narai one last time in a partial solar eclipse observation. The King died in July that same year. His successor distrusted Europeans and expelled all of them from his Kingdom. Wat San Paolo was deserted. Nowadays only a part the original tower stands in ruin.

Rattanakosin – King Mongkut

Modern astronomy came back to Siam around 150 years later. Meanwhile Ayutthaya had been destroyed and eventually replaced by a new Kingdom of Rattanakosin.

Many people would know King Rama IV as King Mongkut, from the musical, the King and I, but the real historical figure was quite different from his fictional portrait. King Mongkut was a real scholar. His knowledge of traditional astronomy was evident in his invention of a very accurate lunar phase calculator still in use today.

King Mongkut studied modern astronomy in depth using textbooks imported from Victorian England. He became expert enough to establish a local Siamese meridian and used it to keep a standard time many years before the international acceptance of Greenwich Mean Time. The King’s standard time was the basis for his successful eclipse calculation.

The eclipse that King Mongkut predicted was the August 18, 1868 total solar eclipse which passed through India and Thailand. This was the eclipse that a French astronomer named Pierre Janssen observed in India and found the first evidence of Helium in the Sun before the element was found on earth.

King Mongkut’s eclipse entourage was stationed at a place called Wa Ko. The eclipse took place just as the King predicted. A group of French astronomers who set up camp nearby witnessed the eclipse and confirmed the King’s calculation as well as the sighting of the helium line. Among them were Georges Rayet, who later worked on the Wolf-Rayet stars, and Edouard Stephan who gave his name to Stephan’s Quintet galaxies.

The eclipse was King Mongkut’s great success, but it also marked the end of his reign. The King contracted malaria and died in Bangkok a month later. To be succeeded by his eldest son, King Rama V, or King Chulalongkorn.

King Rama V

Just 7 years later, in 1875, another total solar eclipse was to be visible in Siam. The new King followed his father’s footstep by inviting British and French astronomers to send expeditions to Siam.

In response, Sir Arthur Schuster of the University of Manchester led a Royal Society team to Siam and together with members of the Siamese Royal family observed the eclipse in Phetchaburi. The expedition’s achievement during the eclipse of April 6, 1875, was to prove the existence of calcium in the chromosphere and prominences for the first time ever.

Schuster was assisted by another British astronomer. His name was Captain Edward Loftus. He came to Siam at least one year earlier to observe the transit of Venus in 1874 and had set up an observatory nearby.


The reign of King Chulalongkorn ended just after the turn of the 20th Century. I also end Part 1 of the History of Modern Thai Astronomy at this point.

In Part 2 I will tell you about how modern astronomy impinged us in Thailand in the 20th Century and what we are doing at present. The episode will be released on October 23rd, 2009. So until then, this is Visanu Euarchukiati in Thailand saying good bye to you in Thai – Sawatdi Khrap.

End of podcast:

365 Days of Astronomy
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