François Terby: a Leuven amateur astronomer 140 years ago
Much as a surprise to many Leuven inhabitants today, once upon a time, all the way back to 1884, there lived an avid amateur astronomer called François Terby in Leuven. He invested serious money to build a 3-story observatory (brick walls, wooden dome) next to his house in the Bogaarden street.
His observations were mainly planetary, Jupiter and also Mars. Many drawings are available, and he corresponded with Schiaparelli in Milan about the ‘canals’ on Mars. His enthousiasm was such that he also could confirm these so-called-channels.
Other observations were around Jupiter and Saturn. He noticed a special effect on Saturn’s ring system, which has been named “Terby’s White spot” after his observations.
On May 23th 2025, I could visit the Leuven city archive, and some surprises came up (tnx to Mrs. Liesbeth Croimans) :
- The 8″ refractor telescope was always called by Terby himself as a “Grubb” telescope, now it is unmistakenly mounted on a Thomas Cooke telescope mount as can be seen on the pciture below.
- The observatory was not just a simpel roof add-on, but a substantial seperate brick tower, including a proper foundation and a wooden dome, about 4 meters in diameter.
Now the hunt is on for the lost refractor. In 1961 the observatory was demolished.
The observatory was a brick building – 3 stories high, it was build on the street side to the left of the existing family home ( and not behind the house, or in the garden as previously assumed).
The location corresponds with a small white circular disk, that is visible on a 1947 aerial picture of Leuven (see below).
A picture of the building plans, as available in the Leuven city archive:
It’s not clear from the plans, if the central column was free-standing, or if it was braced as seen in the cross-section (in red, below left) – all the way up to the upper floor. Remarkable is also that the lowest part of the column (below ground) seems to be smaller in diameter. that would make no sense, from an engineering point considering stability.
War Damage?
First messages were that no files were logged for war damage for the address Bogaardenstraat 70 in Leuven. Now it seems that three different files are available, and logged by Mr. Terby ‘s wife after WW I during the 20’s. The finder of these files (I. Jorissen) o consulted these files in the Belgian “Rijksarchief” on June 5th 2025. Ingeborg writes “… the damage was related to arson by the German troops in Augus 1914, damaging two commercial houses in the (now) “Bondgenotenstraat” (nr. 1 and 2 on the corner of the St. Margaretasquare and the “Tiensestraat”). So luckily the damage was not related to the family house in the “Bogaardenstraat”
“we could see in the files that in 1921, it’s his spouse who acts and files the complaints, and that at that time, she still lives in the Bogaardenstraat. The 5 children are mentioned on the files too. The 5th child (a son) François Jean Charles Ghislain, seemed to be interned in the mental warden of the “De strop” institute in Ghent“.
“the other 4 children are all present as inheritants of the father François. They are all unmarried (still in 1923) and live all in the Bogaardenstraat 96. The oldest son is by that time 41. The marriage contract of 1881 does not contain anything specific. (notary: Roberti). A testament could not be found, not in the files of the noatries Roberti anyhow“
Mr. Paul Stroobant wrote a book on François Terby in 1931, with lots of interesting details. It can be consulted online (Google both names). Mr. Stroobant was then a retired astronomer & director of Uccle Royal Belgian Observatory, which he joined in 1891, shortly after the main observing period of Terby.
Main takeways are:
- before the 8″ Grubb refractor Mr. Terby used a 90mm Secrétan refractor. However it appears that between these two telescope, he also used a 108mm Secrétan !
- Terby did not only correspond with letters to the Royal Belgian Observatory, he actually also did some observations there (old observatory in the city).
- he did some ‘shooting stars’ observing also, from Leuven, and this with his friend ‘ingenieur Van Lindt’. He could observe the famous “meteor shower” on November 27th, 1885. He observed 32 shootings stars a minute.
- he could see bright zodiacal light from Leuven centre in 1883
- his interest started during his high school years, in the ‘Josefieten’ (old market), where a teacher had a small refractor
- his oldest son was a math teacher in the ‘Atheneum” in Leuven
Some of the known associations of F. Terby:
- Societé des Spectroscopistes Italiens
- Societé astronomique de Liverpool
- Societé Royale astronomique de Londres
- Member of the Belgian Royal Academy (1891)
- Chevalier in the Leopold ordre 1896
- Officer in the Leopold order 1907
- Membre de la commission de l’observatoire Royal de Bruxelles 1889
However! not one single word on the destiny of the Grubb telescope.
Also no pictures are know today of the observatory tower.
This picture comes from an RAF aerial survey in 1947. The observatory dome can be identified as a white disk (more a spot actually) on the location in the Boogaardenstraat. before it was clear that the observatory tower stood to the left side of the current house, the location was a bit odd, as the expectation was that the observatory dome would be in the garden behind – or simply on the roof or backside of the house.
On “terby’s White spot”
This concerns a ‘white’, or less dark, spot on Staurn’s ring, near the shadow of the planet. It’s porbably related to a contrast effect.
In this Reference, Monthly Notices of the Royal Astronomical Society, Volume 49, Issue 7, May 1889, Pages 388–389, https://doi.org/10.1093/mnras/49.7.388 Published 10 May 1889, English astronomers try to find the ‘famous’ whit spot but they do not succeed observing it on several nights.