Alexandru i can show you the backfocus on my SpaceCat 51 (same as RedCat 51, just silver finish instead of red) and an ASI 1600MM Pro. In the attached image, you can see the 55 mm backfocus, which is achieved by summing up the widths of the 11 mm and 16.5 mm adapters (both came with the 1600MM Pro), the 20 mm filter wheel and the 1mm adapter (came with the EFW) and the 6.5 mm sensor plane distance relative to the edge of the camera.
The 178MC (which i do own as well, but use only for planetary on an SCT with about 2000 mm focal length) has an M42 thread (the thread inside the red ring of the camera body) and also comes with a T2 nosepiece. The nosepiece has the same diameter as the guide camera on top of my SpaceCat 51 (see the arrow pointing to the helical focuser).
Just on a side note: the EFW comes with a T2 adapter that allows you to attach any camera with a T2 diameter to it, just like the helical focuser in the image.
So in general, it is possible to attach the 178MC to that scope, with some additional adapter rings in between.
But – i would highly recommend, that you tell us, for what type of imaging you want to use the 178MC and the RedCat together. From my personal point of view, those two do not fit well together because the 178MC is not the best camera for guiding but rather for planetary imaging or an allsky camera usage. The RedCat is a wide-field scope, that is well suited for larger nebulas, but you won't be happy to shoot planetary or galaxies with it. But well… just my 2 cents.
Olli
