Controller-General of Finances
Rømer's explanation of the difference between predicted and observed timings of Io's eclipses was widely, but far from universally, accepted. Huygens was an early supporter, especially as it supported his ideas about refraction, and wrote to the French Controller-General of Finances Jean-Baptiste Colbert in Rømer's defence. However Cassini, Rømer's superior at the Royal Observatory, was an early and tenacious opponent of Rømer's ideas, and it seems that Picard, Rømer's mentor, shared many of Cassini's doubts.