I am using the ASI2600MC AIR (same camera and guide sensor as DUO) on an ONTC 800/200, and recently purchased the Starizona Nexus .75 reducer Coma Corrector without realizing that it claims to have an image circle of 28mm (APS-C size), while the onboard guide camera on the ASI2600MC AIR/DUO officially needs an image circle 43mm. So according to the specs this combination should not work. But in fact the guiding was just as good as always even when using an Optolong Ultimate filter, below .5 arcsecs on average mount Rainbow Astro 135E. So the onboard guide camera seems to do quite well even when not fully illuminated... YMMV
📷 M31 First light with Starizona Nex... (2nd session with Starizona Nexus .75 CC on ASI 2600MC AIR + Narrowband Optolong Ultimate)
