On this day in history, November 11, 1851, Alvan Clark, of Cambridge, Massachusetts, received a patent for the telescope. Although not the first person to invent the telescope, he did make some improvements to the device. Due to his background in portrait painting and astronomy, his artistic eye allowed him to locate the flaws in glass lenses.
Yesterday: Windshield Wiper Is Patented
Clark became involved in telescope making at the age of 40, and in 1846 he founded the firm Alvan Clark and Sons, which primarily ground lenses for some of the largest refracting telescopes of the 19th and early 20th centuries. In fact, the firm built the world’s largest refracting telescope five times over.
According to Clark’s patent, the usual method of constructing telescope eyepieces at the time was to make a series of tubes fitted or connected together by screws at or near the places where the lenses were situated. Clark claimed that it was quite an inconvenience to separate the tubes from one another and unscrew the confining screws of the lenses for cleaning purposes. In addition, it subjected the eyepiece to potential damage.
In the patent, Clark stated:
In my improved eye-piece I have not only sought to avoid such dillieulties, but to make a simple and substantial eye-piece and one wherein ready access may be easily had to the glasses or lenses in order either to cleanse or repair them, as the case may require.
To rectify the issue, his patent describes an eyepiece of two tubes, made to fit and slide closely into the other. Each glass is supported within a ring or frame whose external diameter is equal to the internal diameter of the inside tube. The slots through the side of the internal tube were also designed large enough for any person to pass a suitable cleaning device though it.
The internal tube is then to be inserted within the external tube, by pushing down against a shoulder far enough to permit an eye-hole cap to be screwed into it.
