Playing around with my mirror lens on micro 4/3 again, this time with an aluminized mylar filter for solar work - gives a yellow tone which is "nicer" than the white of a more accurate filter.

Four sunspots are visible, but there is also a circular mark which is an artifact, probably grunge in the lens or on the sensor. Picture 1 is the best of 15 or so images, picture 2 is the same image with labels, picture 3 was taken separately with the camera in a slightly different position, showing that the four spots are real since they are still in the same position relative to the disc of the sun, while the round mark is in the same position on the frame but a different position relative to the sun.