Huygens discovered also that an object placed in the common focus of the two lenses of a Kepler telescope appears distinct and clearly defined.

The micrometers of Malvasia, and later of Auzout and Picard, are the development of this discovery.
Malvasia's micrometer, which he described in 1662, consisted of fine silver wires placed at right-angles at the focus of his telescope.
As telescopes increased in power, however, it was found that even the finest wire, or silk filaments, were much too thick for astronomical observations, as they obliterated the image, and so, finally, the spider-web came into use and is still used in micrometers and other similar instruments.

Before that time, however, the fine crossed wires had revolutionized astronomical observations.

"We may judge how great was the improvement which these contrivances introduced into the art of observing," says Whewell, "by finding that Hevelius refused to adopt them because they would make all the old observations of no value.
He had spent a laborious and active life in the exercise of the old methods, and could not bear to think that all the treasures which he had accumulated had lost their worth by the discovery of a new mine of richer ones."(1) Until the time of Newton, all the telescopes in use were either of the Galilean or Keplerian type, that is, refractors.

But about the year 1670 Newton constructed his first reflecting telescope, which was greatly superior to, although much smaller than, the telescopes then in use.