One of the most inexpensive accessories you can get for your telescope is the Baader AstroSolar safety film which you can use to safely observe and photograph the sun. Baader also has the 540nm-pass “Solar Continuum” filter to improve the definition of some solar features, so I thought I’d run a little experiment to see exactly what this filter (which actually costs quite some more than the AstroSolar film) can do for me and also try out some other filters to see whether I can get better results than using the AstroSolar film by itself. Note that the AstroSolar film covering the front aperture of your scope in full is mandatory – a filter alone at the eyepiece side of the telescope is not enough to prevent instant blindness or the destruction of your imaging sensor.
I used my Skywatcher Evostar 80ED with a full-aperture Baader AstroSolar visual film and a 2x barlow with a full-spectrum Canon 600D. Narrow-band filters like the Solar Continuum would work better with the AstroSolar photo film (allowing shorter exposures), but that seems to be out of stock right now in the UK at least, so if I obtain it in the future I might update the article. In any case, for each filter tested below, I shot a few full frames of the solar disk, of which I stacked 3-4 to reduce noise, and also a short video in 3x Digital Zoom video mode stacking about 250 out of 1000 frames after converting it to grayscale and having the same wavelet sharpening applied to all cases.
Since I was using a full-spectrum modified DSLR, the UV/IR filter is the “no additional filter” equivalent case. So this is what the AstroSolar film can do by itself at the visual part of the spectrum: