Anyway, an imaging run I was looking forward too; I purchased my second CaK PST at the weekend with a view of making a double stack CaK filter. Walter and myself had been discussing this as a viable possibility for sometime, and then last month and a trip over to Appenzellerland and we were able to test the theory out. The results from his Basler camera and spectrophotometer showed stacking a CaK PST and Lunt filter worked, so I was optimistic my CaK double stack would work.
This shot was taken with the 70mm scope at f6 with a DMK31 camera. Conditions were less than ideal, I was shooting through my open front door, the sun was at less than 10 degrees altitude and there was pretty thick haze.
DS CAK full disk bw by Mark Townley, on Flickr
Ok, so what is this showing? Well, a pair of 2.2angstrom filters stacked gives us a 1.5 angstrom filter. Like a double stacked Ha filter a DS CaK lets through less continuum leakage, as a result what struck me is that the plage and supergranualtion seemed slightly brighter and more evident than normal 2.2a CaK. I've included the last CaK full disk I took from back in august, as think this shows the subtle differences.
CAK FULL DISK BW by Mark Townley, on Flickr
I'm looking forward to exploring the possibilities with this filter, and, the weatherman has just given out warmer and sunnier weather for the weekend, fingers crossed!
Hope you like.
Mark
wow this is a fantastic full disc Mark 
If I hear of another alexandra i'll give you a shout.
hmy: 
