In the generation after Galileo’s pioneering discovery of Venus’ phases, early adopters of astronomical telescopes were disappointed when their instruments revealed essentially nothing more about the planet. It remained an impenetrable mystery, a dazzlingly white disc marred by the false rainbow of chromatic aberration. What was Venus? Was it just a mirror of the sunlight that illuminated it? What was its nature that made it so reflective? Imperfections in the glass from which telescope optics were then made further distorted planetary images, yielding spurious flares, shadows, and haloes. What was real, and what was not?