History of the telescope
The earliest known telescope appeared in 1608 in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
Mount Wilson Observatory
The Snow Solar Telescope was the first telescope installed at the fledgling Mount Wilson Solar Observatory. It was the world's first permanently mounted solar telescope. Solar telescopes had previously been portable so they could be taken to solar eclipses around the world. The telescope was donated to Yerkes Observatory by Helen Snow of Chicago. George Ellery Hale, then director of Yerkes, had the telescope brought to Mount Wilson to put it into service as a proper scientific instrument. Its primary mirror with a focal length, coupled with a spectrograph, did groundbreaking work on the spectra of sunspots, doppler shift of the rotating solar disc and daily solar images in several wavelengths. Stellar research soon followed as the brightest stars could have their spectra recorded with very long exposures on glass plates. Today the Snow solar telescope is mostly used by undergraduate students who get hands on training in solar physics and spectroscopy.
It was also used publicly for the May 9, 2016 transit of Mercury across the face of the sun.