highest accuracy.

George Biddell Airy, Seventh Astronomer Royal,[4] commenced his
Greenwich labours in 1835. His first and greatest reformation in the
work of the observatory was one he had already established at
Cambridge, and is now universally adopted. He held that an observation
is not completed until it has been reduced to a useful form; and in
the case of the sun, moon, and planets these results were, in every
case, compared with the tables, and the tabular error printed.

Airy was firmly impressed with the object for which Charles II. had
wisely founded the observatory in connection with navigation, and for
observations of the moon. Whenever a meridian transit of the moon
could be observed this was done. But, even so, there are periods in
the month when the moon is too near the sun for a transit to be well
observed. Also weather interferes with many meridian observations. To
render the lunar observations more continuous, Airy employed
Troughton's successor, James Simms, in conjunction with the engineers,
Ransome and May, to construct an altazimuth with three-foot circles,
and a five-foot telescope, in 1847. The result was that the number of
lunar observations was immediately increased threefold, many of them
being in a part of the moon's orbit which had previously been bare of
observations. From that date the Greenwich lunar observations have
been a model and a standard for the whole world.

Airy also undertook to superintend the reduction of all Greenwich
lunar observations from 1750 to 1830. The value of this laborious
work, which was completed in 1848, cannot be over-estimated.

The demands of astronomy, especially in regard to small minor planets,