The attached image is a staked raw capture for M_34. I noticed many hallos in the image. I think post-processing can take it out, but any idea what caused it?
I'm not sure, are we talking bloated stars or these big "circles" around the center of the image?
Dew/ice on the lens comes to mind. If so, a dew heater can prevent that from happening. Another possibility is a less than perfect lens. If that's the issue, you could try a UV/IR filter to prevent bloated stars.
Are there any light sources close to the scope? Scattered light might enter the scope and make its way to the sensor.
I’m talking about halos all over the picture… stars expected to be big at f/10. Temperature can drop at night below 0C but I have the dew heater on. Do you maximize the dew heater level at winter?