Dated to around 1660, half a century after Galileo's discovery of the phases of Venus and the moons of Jupiter, Dou's astronomer works the old-fashioned way, from a book and a celestial globe.
The website's background image is cropped. The painting, at the Getty Museum, Los Angeles, is is smaller than you might think (barely 8 inches wide). It's believed that Dou would used a magnifying glass to paint in such detail. Thus his painting used state-of-the-art technology that was ignored in the subject itself.