Flats question

[DaveNL]

As stated previously, I am new to the Atik 460EX mono and to CCD camera in general (so be gentle!). I have been taking flats using a light panel. Lots of dust motes! Much more (and more prominent) than what I am used to with a DSLR.

I've been aiming for 1/3 to 1/2 histogram. Using Lumicon Deep Sky filter that turns our to be about 3 sec, and for OIII filter about 10sec. For Ha (7nm) that turned out to be around 90sec but I rolled that back significantly because the Ha flat @90sec looked terrible (motes too dark, black border around the edges). Does this sound about right?

My first time through processing (in PI), I'm still seeing some signs of the dust motes in the integrated result. Not sure if this is processing shortcomings (ie. PI operator shortcoming  ), or problem with flats. Attached is master Ha flat.

Any suggestions appreciated.

Dave N

[jcinpv]

Dave, I am using a 460EX color. Taking flats in sunlight with a white T-shirt tightly wrapped over the C8. Exposure down to 0.1s to get a 1/3 hump on the histogram.
My flats show a lot of dust motes - more than I like. But I have the same situation with my Atik Infinity.
As to PI, I've found it quite difficult (as a new user myself), to get good results with the BatchPreProcessing script.
When I add flats to the mix (and I just took a new set), I seem to have twice as many dust motes - almost as if the set of flats are flipped vertically from the lights.
Using Nebulosity 4 to stack doesn't properly eliminate all hot pixels.
Using the Atik Dawn app doesn't help any because when I save the result all the color is stripped out.

John C