Hi Rob,
Looks like you are getting Newtons Rings in your images.
https://en.wikipedia.org/wiki/Newton%27s_rings
This is quite common though when shooting in H-alpha and is caused by reflections from the little glass window covering the sensor of the camera.
There are a few things you can try to sort this out.
1. Try tilting the camera somehow. There are actually tilt adapters you can buy for just this purpose but you may get away with a slight bit of tilt in the eyepiece holder if you can.
2. Try taking flats by defocusing on the disc of the sun and taking a short avi of that, around 300-500 frames. You then create a master flat and add it to the stack.
3. Use a bit of drift or dithering.
Let the sun move around slightly on screen, it doesn't have to be much but I find I really only get newton rings when I have perfect alignment.
Generally I just guesstimate alignment by roughly plonking the tripod in the right area, it is good enough to tack the sun for an avi but still has enough movement to knock the NR's on the head.
