I did do some UV solar imaging with the Baader Solar film previously. Unfortunately, the one Solar film I have is for solar viewing (not the photographic version), which does reduce the light passing through to the camera significantly. Hence I have had to use higher ISOs and slower speeds for imaging when using the Baader U. Hence I thought it would be good to try this again now that I have the Baader Herschel prism, to see if enough UV is passed through to the sensor.
Equipment used: full-spectrum Olympus E-PL5, Skywatcher ED80, Baader Herschel Prism, Celestron 1.25″ Ultima 2x APO Barlow, Baader U filter and no ND filter. It was possible with this setup to shoot at ISO 200 and up to 1/2500 secs (over 7-stops of extra light compared to the Solar film).
The following images have had the white balance adjusted to have false colour.
Another Baader U solar image taken 4/10/14:
I suspect that if I used a 2x teleconverter lens which transmits UV well, then I would get better results than I have managed. I will also try this with my friend’s Skywatcher ED100, to see if it makes a difference.
The other thing to note is that although the Baader U passes light through into the region of the Calcium K-line (394nm), this is only a very tiny amount compared to the rest of the UV. So while it will capture the details within that area, it will not be able to do so to the level of the dedicated Baader Ca-K line filter (which happens to be a very costly double-stacked filter).