Flat problem with dust

Adrian Dan Cioc

Hello,

Recently I made the transition from CCD to CMOS mono sensor (Moravian Instruments C3 26000 pro). My last camera was also a Moravian with a shutter and I got used to longer flat exposures, as to not catch the shutter closing during the exposure. Don't know if it's important for CMOS or not, but I thought I should mention.

So I started a new project, and my lights would not calibrate. I tried 2 times, one time with dark optimization enabled and without in WBPP.

With dark optimization enabled, the resulting calibrated images are like a flat with just about 100 stars in it ... not good (image registration fails in WBPP).

Without dark optimization, I get a master light (nebula and star present) but with 2 dust motes present (when only 1 is obviously pronounced in the flat). The second one seems like a mirror of itself.

I attached a print screen of one of the flats. The dust pattern is fixed, all the flats look the same. I take flats every session.

Should WBPP be having trouble with my flat? If I look closely, it seems there are two dust motes superimposed, that would explain the contrast.

BlockHead

Hi Adrian,

First do not optimize darks that calibrate lights. This is bad. A bias frame or short matching dark should be used to calibrate the flats. As you saw... doing otherwise is bad medicine.

If you blinked your images and the dust motes do not move between the flats... then either your optical system changed between the flats in some way... of your flats are rotated with respect to the lights. 

I think you need to show some images of your calibrated lights. Screenshots should do it. If they are dark in the calibrated images..that is a good sign. 

-the Blockhead