ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Drum chronograph, Sydney Observatory, Sydney, Australia. This observatory was established in 1858. This is a 4-pendulum drum chronograph, with the four pendulums at right and a cylinder of recording paper at left. The pendulums and rotating gear system (lower left) ensure a steady rotation that can be adjusted to a faster or slower rate. A pen (centre left) traces a mark on the paper wrapped around the cylinder, providing a graphical record for events and the time at which they occurred. This device would have been used with a transit instrument to record the timing of astronomical observations.
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