Plot of total intensity of Crab pulsar against time in the four observing sessions shown separated by dashed horizontal lines. The left panel corresponds to the band centred at 116.75 MHz, while the panel on the right is at 157 MHz. The elapsed time shown on the vertical axis is the observation time within each session. The vertical axis is labelled with the hour angle of the Crab pulsar on the right side of the second panel and corresponds to the middle of the 15-min observing sessions.