OBSERVING IS SUBJECTIVE Wilhelm Tempel's Crab Nebula sketch comparison between six prominent 19th-century astronomers. Clockwise from top right, the sketches were made by J. Herschel, D'Arrest, Lassell, Secchi, Lord Rosse, and Tempel. 32 FE B RUA RY 2 019 * SK Y & TELESCOPE WILHELM TEMPEL / KÖNIGLICHE BÖMISCHE GESELLSCHAF T DER WISSENSCHAF TEN Crab Nebula