The dark sunspots are not dark really, they are just cooler than the surrounding area. The surface temperature of the sun is around 5770 degrees Kelvin whereas sunspots are around 1000 degrees Kelvin, that is still very hot! Sun spots are caused by the suns internal magnetic fields breaking through the surface and cooling the gasses.

200mm F5 Newtonian telescope on a EQ 5 mount. Starlight Xpress MX716 CCD camera

3x1000ths of a second exposure. Processed with Starlight Xpress software and Registax