Solar radiation is strong. Following problems for solar telescopes may be telescope site selection and temperature control.
I wonder the telescopes themselves and their instruments are different?
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Solar telescopes are optical telescopes, and it is quite possible to use an optical telescope to observe the sun. The usual way is to use the telescope to project an image of the sun, by placing a card at the focus of the eyepiece.
A professional telescope is a complex piece of engineering, it is designed for a particular task, such as observing very faint objects. It isn't designed for solar observation, and would most likely be rapidly damaged if it were pointed at the sun.
Solar telescopes have plenty of light to observe. The technical challenges involve controlling that light, so that it doesn't damage the equipment, and filter it, so particular aspects of the sun can be observed. The engineering problems of a solar and "nocturnal" telescope are different, so you can't use the same professional telescope for both. Analogy: an F1 race car and a rally car are similar in some ways but have been designed to overcome different technical challenges. An F1 car would never win a rally, nor would a rally car win at F1.
I might be answering out of turn, but nobody (so far as I noticed) has mentioned the "Dobsonian Sun Telescope", which a Newtonian design that uses a full-aperture plane two-way mirror as secondary set at 45 degrees, that reflects 95% of the sunlight away from the optical path. This is a safety feature, should it be broken, the secondary mirror will also be broken as the optical path is disrupted. The Primary mirror is unsilvered / unaluminised. There is also a welders' glass in the optical path. http://planitarium.net/sfsa/sunscope/