Finally got out in the backyard and got some photons. Not a lot of data yet and my O3 data had issues - much more bloated than the Ha and oddly suffered from some kind of radial distortion (coma?) unlike the Ha. It could have been the slight defocusing of the guide camera (in an OAG) when the O3 filter refocussed. Weirdly the 3nm O3 filter needs much shorter flat exposures than the 5nm Ha? Is that normal? Anyway, despite the poor O3 stars, I scraped together a quick HOO image:
https://www.astrobin.com/full/408897/0/
5nm Ha 40x180s, 3nm O3 40x180s shot though an 8" Quattro on an EQ6-R with a ZWO ASI1600MM-Pro.