I use a C8 and QHY8 Pro. Get the Feathertouch focusser for the Hyperstar, makes life much easier. Comments similar to Peter's. The f2 data collection speed makes up for the limited 8" aperture quite well. Pity about the months of cloud we've had here in Brisbane, as I'm trying to do SMC and LMC widefield with both Hyperstar and ebay el cheapo Pentax 135 Takumar piggy backed. Yes, I've got an SMC Tak on the way, but this one's not bad for $30 or so. Recommend this setup for UWF. Finally got some M45/42 Pentax shots last night. Hyper was on 26 Nov.
Attached are M42 20x5 seconds Hyperstar and 20x30 secs P135 for comparison, both with simple Nebulosity DDP and no cropping. Also a couple of shots showing setup and my simple sheet plastic "lens cover" for hyperstar, as the normal one don't fit
I also made a lens hood for when I use the Hyperstar, attaches to the Velcro ring. Stubby coolers make great lens hoods for finder scopes, too. Keeps dew away so far.
Summary: A very good asset. BTW, not liking the idea of eternally swapping Hyperstar and SCT modes, I finally bought a second used C8 OTA and keep one with Hyperstar and the other with f6.3 reducer and rear remote FCUSB electric focusser setup. The extra OTA cost was worth it for the quick swap out convenience.
Very little cable-induced diffraction spikes, I put the two QHY cables at right angles to try and imitate a Newt, but the spikes are very faint anyway. Can you see them on the CHQ jpg?
I use a matt whiteboard on the obs wall for taking twilight flats with the Hyperstar, a little easier than the T shirt when you have a camera there.
Next toy to get is a GSO 10" RC to replace the 8" SCT for the deeper stuff.
Enjoy your Hyperstar.