unsuccessful optical search for PSR 1919+21
optical pulsations from the Crab pulsar 
optical data before radio discovery not analysed 
X-ray detection on rocket experiments [11, 7]
X-ray data before radio discovery not analysed 
Figure 3: The Crab pulsar. This pair of photographs was taken using a stroboscopic technique, showing the pulsar on (left) and off (right). From Lyne & Graham-Smith 1990 .