I am shooting my images with my ZWO ASI071MC Pro, which is an OSC ("one shot color") camera.
I have some doubts whether I am applying my flat frames correctly.
White images coming directly from the camera have a strong greenish color, as they are not white calibrated yet, so also all my flats (taken with a pure white flat field box) are quite greenish.
I have now three options:
- take the flat frames as they are (greenish) and apply them in Pixinsight. I doubt that this will lead to good pictures.
- color calibrate the flat frames before applying them. (how?)
- shoot flat frames in black&white mode (this is possible e.g. in Sharpcap)
So far I used option 3, but I do not known if this is a good idea to apply a black&white flat frame to a color image.
Anyone any ideas?
How do you process your OSC images with flat frames?
Thanks, any help is highly appreciated!
With OSC color camera you have to:
1. attempt to have a uniform/non-gradient light for taking the flat frames (there are some "neutral" EL-panels too on the market) or shoot night-sky flats (twilight etc.)
2. check the lowest ADU value in the corners and compare to the highest ADU in the middle of the FOV so as the range of your vignetting is "reasonable"
3. you have to check it for all 3 colors R G B... if you manage to get a reasonable variation for all 3 colors in corners/center of the FOV then you may be OK with taking 1 set of flats for whole picture
4. if you have some problems (can't calibrate in some of the 3 color channels) you have to split the bayer planes into 4 - making a 4 set of raw fits referring to R G G B pixels and use this MONO 4 channels to calibrate for vignetting...
BTW I do take 5 second long flats with my ASI094 but my uniform light EL-PANEL is on the absolute minimum of its brightness (am using F/3.6 BTW).