He was a supporter of Copernican heliocentrism, the astronomical model which positioned the Sun at the center of the universe, with Earth and the other planets orbiting around it.

[4] By his own account, he first observed a lunar eclipse as a schoolboy, on 30 December 1591: it ended at quarter to six in the morning, giving him just time to get to school for his first class at six o'clock.

Intending to study with Tycho Brahe Wendelen set off for Prague, but was stopped en route by an illness that necessitated his return to the Low Countries.

[7] It was while at Geetbets that he published Loxias seu de obliquitate solis (Antwerp, Hieronymus Verdussen, 1626), a critical overview of ancient and medieval astronomy.

In 1633 he was also assigned a prebend in the collegiate church of Condé, to provide an income that would support his scientific work.

In 1652 his Teratologia Cometica, containing a defence of heliocentric astronomy, was printed in Tournai, dedicated to Jean-Jacques Chifflet.

Pierre Costabel states that the scholarly world learned of Wendelen's discovery in 1651, when the Italian cleric and astronomer Giovanni Battista Riccioli (1598-1671) published his book Almagestum novum ...

On the same page (center of right side), Riccioli again credits "Vuendelinus" with showing that Jupiter's moons obey Kepler's third law: "… ita Planetulorum Jovialium distantias a Jove, esse in ratione sequialtera suorum temporum periodicorum."

[13] Original : 4) Confirmatur vero fides hujus rei comparatione quatuor Jovialium et Jovis cum sex planetis et Sole.

Etsi enim de corpore Jovis, an et ipsum circa suum axem convertatur, non-ea documenta habemus, quae nobis suppetunt in corporibus Terrae et praecipue Solis, quippe a sensu ipso: at illud sensus testatur, plane ut est cum sex planetis circa Solem, sic etiam se rem habere cum quatuor Jovialibus, ut circa corpus Jovis quilibet, quo longius ab illo potest excurrere, hoc tardius redeat, et id quidem proportione non-eadem, sed majore, hoc est sescupla proportionis intervallorum cujusque a Jove: quae plane ipsissima est, qua utebantur supra sex planetae.