Had a sunny morning with moderate seeing. We haven't seen a lot of sunny days this summer. So I cycled through some equipment, which might be interesting for anyone thinking of buying or making one of these things.
1. Coronagraph made from a modified Baader prominence viewer with a 50mm objective and using a 10 Angstrom H-alpha filter. Great view of 20 tiny prominences around the circumference of the Sun. Despite the upper atmosphere smoke in the northeast, the background around the Sun was pretty dark. The proms were so small though, that I did not go for other wavelengths (H-beta, H-gamma, helium D3).
2. 155mm f/7 apo (AP155EDF) with a Quark double stacked onto a Lunt modular double stacking unit (normally for the LS80 and similar), Baader DERF. The double stack on the Quark makes the field dark and the view narrow. But what is there is high contrast, and you could see the active regions very well.
3. 155mm f/7 apo (AP155EDF) with a Quark (single stack), Baader DERF. Brighter and wider field of view. The disk is more washed out but the small proms were nice.
4. 155mm f/7 apo (AP155EDF) with a Lunt 2" solar wedge. Had trouble getting my binoviewer to focus but eventually got it. The biggest sunspot did have a zebra pattern in the penumbra, so it was pretty good. The granulation was obviously there but not detailed. More like mottling.
5. C11 with a Quark double stacked onto a Lunt modular double stacking unit, Aries ERF. Very small field of view and dark, but did show the active regions.
6. C11 with a Quark (single stack), Aries ERF. The proms were the best here of all the scopes. High power but still bright. Not perfectly sharp due to the seeing, but still brought in the most detail overall. The disk was again washed out but you could find the active regions.
7. C11 with Baader visual solar film. Very impressive white light view. The granulation seemed so clear and faculae were all around. Yet the sunspot showed less of a zebra pattern. I realized that the reason it looked so good was that I could get 24 Panoptic eyepieces to focus in the binoviewer, leading to a good low power with almost the whole Sun in the field of view. Versus the AP155, where I had to Barlow the image to get to focus.
8. LS80 DSII (with circular polarizer filter and bright blocking filter). The most beautiful disk. Every detail from GONG right there and more. Bright disk. Dark background. Not high power, but great full disk.
#2-#8 were all binoviewed.
My conclusion: If you happen to own a C11, get some Baader solar film for it. With a binoviewer, it is just an amazing view even if seeing is not perfect. And for proms, big aperture really helps, too. You will need an expensive ERF; mine is from Aries.