Kyuzumaki

I’ve got a Heavy setup already but recently bought a Skymax 120 as I want to have a more portable mount for trips or just if I need to move for a low target I can’t easily get from the shed. I looked at the AZ gti but after reading around I think it will not live up to my expectations so I’m going to make an onstep controller and run some nema 17 motors instead. 
 

My main question is are there any relatively cheap manual mounts I could use as the basis for this? I see a lot of eq1 and astromaster mounts second hand. But I’m pretty sure the Dec axis at least on the eq1 is not a worm but a push rod of some sort so doesn’t rotate the full 360 degrees. I can’t work out from photos is the astromaster does or not.

Are there any of the cheap mounts that have true dual axis drives I could pick up?

Is this not just cosign error? The stars in all corners are slightly oval, if this is the problem and you have a different camera with a smaller sensor it should disappear.

Only other suggestion is possibly the sensor is slightly off axis? So closer to one edge than another. You could spin the sensor around and see if it rotates on the centre pixel or slightly off centre