For thousands of years Saturn marked the edge of the known solar system, until a teenage military deserter who made his living playing the oboe doubled its size in a single night. This episode follows William Herschel from the Battle of Hastenbeck, where his father told him to flee, to Bath, England, where he became organist at the Octagon Chapel, composed symphonies, and fell into astronomy through Robert Smith's books on harmonics and optics. It explains why glass lenses suffered from chromatic aberration, why Herschel ground speculum metal mirrors for up to 16 hours a day, and how eliminating the secondary mirror in his Herschelian design saved precious starlight.

The heart of the story is the partnership with his sister Caroline, who recorded his shouted observations by candlelight, discovered eight comets with her own sweeper telescope ...