I recently purchased a Baader K-Line CaK filter for ultra violet images of the sun. I'm in the process of making a hybrid filter using elements from a CaK PST to narrow the bandpass of the standard filter. I'm currently using ND3.8 film as the primary filter, though shortly are hoping to use this filter in conjunction with a bespoke Herschel wedge. Fingers crossed this is currently being assembled for me by an engineer in Italy. The plan will be to use this wedge to image solely at CaK wavelengths and should afford faster shutter speeds than i'm currently getting with this setup.
There is currently nowhere near the contrast achieved by the CaK PST, however by using the Baader K-Line and optical elements from the CaK PST should improve things considerably. I will then be able to use this setup with my 70mm and 127mm refractors and afford considerable improvement in resolution, without the 100mm CaK aperture limit imposed if I were to use a Lunt CaK wedge. As always, stay tuned for updates!
