Optical Timing of the Pulsar NP 0532 IN the Crab Nebula

Times of arrival of pulses have been measured for NP 0532 during the period 1969 December 15 1970 May 3. A good fit could not he obtained to all the data at once, but good fits were obtained after dividing the observing period into four unique intervals. This may indicate sudden events in the pulsar which produce changes of the order of one part in 10g in the pulsar frequency and four parts in 105 in the rate of change of frequency. In each case the data imply a slowdown of the pulsar. We found that the average value of the "braking parameter" n in the equation dE/dt = A w was 3.63, but dividing the data into shorter intervals gave values between 0 and 5.