Last night I got an opportunity to get outside and sort some photons.
Attached is the first spectrum from this rig in my C11. The arrangement was exactly as shown in the photo in the first post, and the dispersion achieved was 4.78A/pixel.
Compared with previous spectra of Sirius that I'd collected with the C8, there is a significant improvement in resolution. There was a visible artifact in the original AVI, however, which was still there in subsequent sequences of stills (yet to be processed). It manifests itself as a faint trumpet shaped halo broadening toward the blue end of the spectrum, but I'm pretty sure it's not focus. I think it might be an artifact from the focal reducer, so I'll do some experiments to see what I can do about it... but the end result suggests it is not a big problem.
Measured Planck Temperature for this spectrum is 12000K. I must check what the official temp is...
Al.