As the guys say, Best way to image the Sun is by taking a video with said camera (DMK21 etc) and then use registax freeware to pick out the best frames and stack them together.
The closest I got to prime focus was to unscrew the lens from my Televue 3x barlow (this gives about 1.5x) - pop it into the eyepiece holder of the pst then put the DMK on top. These lower powr lens only systems are available in europe heres the type of thingy to look for... With this you may also get focus with DSLR
http://starizona.com/acb/15x-Piggy-B...-P1317C80.aspx
what type of cam are you using??
BTW theres a nice active region (sunspot) to get practicing on at the mo. Up here in Ireland at this time we struggle to see the sun at all..
David Gradwell