The Airy Transit Circle

Page 4 of 6

• 1. Airy's advances
• 2. New transit instrument
• 3. Chronograph
• 4. Innovations
• 5. Airy the man
• 6. Find out more
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Innovations

It was not only the observers and the instruments that introduced errors to the measurements made. Once the observations had been made, the measurements would be handed over to the computers or clerks, who in Airy's day, worked at the Observatory from 8 in the morning until 8 at night. Their job was to turn the raw data into useful tables. To ensure that as few errors were made as possible, Airy devised a form to fill out, taking the computer through every step of the calculation. This production line method meant that errors might be reduced or at least be easily traceable. It also meant that someone relatively inexperienced could carry out quite complex calculations.

In the hierarchical structure of Airy's Observatory, the computers were at the very bottom of the heap. Above them came the observers, the chief assistant and at the very top, the Astronomer Royal.

Airy's drive to make the Observatory carry out its job of aiding navigation more efficiently led to other innovations besides the Airy transit circle. One aid to navigation, which had been installed by Airy's predecessor, John Pond, in 1833 was the timeball. To this day it falls at 1pm every day to signal to navigators on the Thames the time at Greenwich, that they might set their clocks accordingly. This had originally been activated by hand - Airy made this automatic.

When Airy first arrived, the work of the Observatory was still very much focused on positional astronomy and although the Observatory was expanding, it was still very small. When Airy finally retired in 1881 there were several new departments, including a heliographic department (for observing the Sun and in particular for making daily observations of sunspots), a spectroscopic department (making use of the latest technology to investigate what stars are made of), and a Double-star department. Certain existing departments such as the magnetic and meteorological department had changed beyond recognition. This department in Pond's day consisted only of some magnetic needles and barometers. But now it had its own buildings and a team of staff tasked with taking daily readings of the direction and intensity of the Earth's magnetic field both in the vertical and horizontal plane, of temperature, humidity and atmospheric pressure, and of wind speed and direction, rainfall and hours of sunshine.

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Published: 2002-07-01