The Sun can be observed with a Lunt Solar Systems hydrogen-alpha telescope that filters out all but one wavelength of red light. An image stacking program called Registax removes a lot of noise caused by Earth’s turbulent atmosphere
Astronomer Rudolf Wolf observed sunspots through a telescope for 46 years from 1847 and managed to reconstruct historical records back to 1610. His sunspot number monitoring work continued at the Zürich Observatory until 1979
The Sun appears deep red to human eyes from a Hydrogen-alpha filter in a solar telescope but they are processed to create a yellow image that is expected by most people