Asi071MC COOL long exposure problem

koal01

Hello, i've been doing 300 and 600 second exposures during my last sessions and i'm noticing abnormal strange black donuts on my frames.

These donuts appears directly when shooting in raws FIT files and the postprocessing does not remove these defaults correctly soit appears to be an issue.

I tested 4 or 5 sessions during two weeks cooling the camera at -10 °C and this problem appears constantly.

I'm shooting with APT and tested unity gain, lower read noise and high range modes and it has no consequences on the problem.

I'm attaching a file sample so that you can see this strange thing and hope someone knows a solution to remove these dark donuts.

Thank you

Mourad

moson

The donuts caused by dust,you can calibrate it with a flat field.

koal01

Thank you it seems to be the case, after hard cleaning mosts of donuts have gone, is there a cleaning kit recommended by zwo to keep the glass protection and sensor clean ?

Thank you

moson

I'm sorry that you may buy the cleaning kit by yourself.