Refracting telescope
Refractors were the earliest type of optical telescope. The first practical refracting telescopes appeared in the Netherlands about 1608, and were credited to three individuals, Hans Lippershey and Zacharias Janssen, spectacle-makers in Middelburg, and Jacob Metius of Alkmaar. Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo then communicated the details of his invention to the public, and presented the instrument itself to the Doge Leonardo Donato, sitting in full council.
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.