Derek,
Many thanks
In the amateur solar telescope scene, things seem to change quickly and move fast.
I have to mention the latest spectroheliograph project from Christian Buil.
His 3D printed Sol'Ex design combined with the excellent INTI software by Valerie Desnoux has the potential to transform the SHG capabilities.
http://www.astrosurf.com/solex/sol-e...tation-en.html
Making use of the very small pixel (<3micron), fast frame Cmos (>300fps) cameras and very narrow entrance slits (10 micron) combined with specially designed collimating and imaging lenses, the early results are truly amazing!!
The solar image can be reconstituted from the SHG scan in less time than it took to type this sentence - 3 sec!!! almost real time imaging.
The future of "cost effective" multi-wavelength solar imaging is close to hand.