The Belgian Jesuit Charles Malapert organized there the observations of sunspots, in which Sylvius took part.
In 1617 Sylvius accompanied Malapert on his return to the Southern Netherlands, where they both spent twelve years at the University of Douai.
In 1630, Malapert was called to Spain to occupy a newly created chair in the Jesuit Colegio Imperial de Madrid.
Sylvius continued on, and subsequently taught at the Colegio Imperial, building the university a planetarium in 1634.
Sylvius left Spain for the Southern Netherlands in 1638, where he stayed in the Benedictine monastery at Anchin, for which he may have constructed its planetarium.