Christiaan Huygens (1629-1695) was a Dutch polymath who is well known in some circles to this day. While he spent some time in France and England, Huygens lived the latter portion of his life in his native Holland. Having commented on religion while living in many different countries, Huygens espoused a personal philosophy similar to many aspects of modern science.
The modern pendulum clock was among his more illustrious inventions. Horology is the study of measuring time, and it became something of an obsession for him. Nevertheless, he’s also well remembered among astronomers for discovering the moon Titan. His contributions to the field of optics made modern telescope construction possible as well.
While his calculations regarding stellar distances weren’t always accurate, they were always interesting. Huygens made a screen facing the sun and from measurements taken with this device, he figured out that the sun was approximately the same intensity as that of Sirius. By taking the angle and diameter of the hole, Huygens surmised that Sirius was 30,000 times further away from the Earth than the sun is. However, Sirius is actually around 500,000 times further away. Huygens didn’t realize that Sirius was several times brighter than the sun. Strangely enough, his calculations were accurate for the data he was working with.