Looking at the Beacon in the rain

 

It rained all the way back from the south. Here is the view of Penrith Beacon. I amused myself by timing the wiper blades. It took 24.28s for 20 cycles. My reaction time on that watch is 0.25s. That means the percentage uncertainty in the reading is 1%. I can just about justify 3sf. One cycle is 24.28/20 = 1.21s. By timing multiple cycles I can justify a time to hundredths of a second even though I am not physically capable of timing one cycle on its own to that precision.