The Great Lick Refractor
In 1609, Galileo Galilei in Italy and Thomas Harriot in England turned a new Dutch
invention—then variously called a truncke, a tube, or a perspective
glass—on the stars. In effect, a telescope gave an observer a much
larger eye in the form of a lens which collected far more light,
concentrating it at a focus. Even the modest increase in brightness and clarity
afforded by the first small telescopes revealed a hitherto invisible universe
full of unimagined wonders.
Astronomers made careful drawings at the eyepiece or used instruments to
measure what they saw. As the size and light-gathering power of telescopes
increased, so did the sophisitication and precision of instrumentation. By the
nineteenth century, the astronomer's toolkit included micrometers for measuring positions,
angles, and angular distances; photometers for gauging luminosities; and spectroscopes
for analyzing starlight. As pre-telescopic observers had done before them, astronomers of
the telescopic era were pushing visual observing to its limits.
Click on the thumbnails below for more on late nineteenth-century visual observing at Lick Observatory.
Drawing of Jupiter