Ah ok I see what you are getting at
The fits viewer settings afaik don’t impact platesolving. However an image taken with the camera using the imaging module of ekos (not the platesolving module) will appear in the viewer and to make it so you can see things you will want auto stretch turned on. If you don’t have it on you can either click the stretch button in the viewer or manually move the sliders at the bottom to brighten things up.
Unfortunately I’ve no experience at the type of focal length/fov you are on about so can only offer hints/ideas/questions. So I may be talking complete rubbish in the next bits…
If using astrodmx to image that will most likely clash with the sv305 indi driver used by ekos so you will probably want to ensure you disconnect it in the indi control panel once pointing in the right direction.
How are you going to be guiding? I’ve tended to use my guide camera/scope to do my polar alignment and also do platesolving to get pointing at my target before switching to my main camera to fine tune things (I’ve got a cheap and cheerful setup so the scopes don’t quite point in the same direction). Could you get close using your guide scope then fine tune with the c5? Not sure if this stops it doing a blind solve but you could at least get it pointing somewhere known.
Have you managed to focus things? I find this the hardest part of my process and I’m at a much shorter focal length. One thing I did find was focusing using astrodmx to display and zoom in was easier than using the ekos focus module.
Finally have you tried without the barlow? This is going to make the image fainter and have a narrower fov which will make life difficult.
I’m thinking of getting a c5 or maybe c6 but probably use a reducer for galaxies etc as the planets tend to be hidden by my house so would be interested in knowing what results you get.
Regards
Nigel