Another thing about running a double-stack Ha set up is that you end up seeing three or four solar images.  The faint secondary and tertiary images are called "reflex" images.  You have to adjust the double-stack knob to move all of these reflex images out of the eyepiece field-of-view, leaving only the brightest "primary" image visible - (something the Coronado double-stack product insert did not mention).  See page 2 in Lunt double-stack Ha manual http://www.luntsolarsystems.com/a/pdf/Double-stack%20manual.pdf - Clear Skies, Kurt