Telescopes had been built to look at the stars, and astronomers weren’t going to ignore the closest example — our Sun.
Usually, telescopes are built to see objects that are too faint and far away to be easily visible. They’re constructed with giant mirrors or lenses so they can collect more light than the human eye can see on its own.
Telescopes designed to see the Sun, or “solar telescopes,” have the opposite problem — their target emits too much light. The Sun is extremely bright, and astronomers need to be able to filter out much of the light to study it. This means that the telescope itself doesn’t have to be extremely powerful; instead, the instruments attached to it do the heaviest work.
Solar telescopes are ordinary reflecting telescopes with some important changes. Because the Sun is so bright, solar telescopes don’t need huge mirrors that capture as much light as possible. The mirrors only have to be large enough to provide good resolution.