Now we’ll create the master flat. We need to select the flats, the masterbias and the BPM will help as well to correct bad pixels in the flats.
I’ll remove the bias frames from the list by clicking all next to the bias button in 1) LOAD, this will deselect them and then press clean to the right of this button. Now the bias frames are removed.
The flats are selected by clicking on none next to the flats button (if they aren’t selected yet).
At the bottom, we need to check if the proper bad pixel map is selected. I’ll use the second one that we created. So I unselect the first. Otherwise the first BPM in the list is used.
And we make sure the master bias is selected as well.
At the master flat settings in 2) CALIRBATE
I use median combination again. If you have 20 flats or more, use average and outlier rejection.
set flat normalization to multipli-scale which is the default and recommended setting
Since I only work with 5 flats, and don’t want them to inject noise in the lights, I’ll choose to blur the flats to reduce possible noise injection. I’ll use 2x 3×3 median.
Click on create calirbation masters, our master flat will be created with the bias subtracted and the BPM and blurring in the flat will make a very smooth flat for flat calibration. Check the statistics again in the header of the masterflat.
From the statistics you’ll see that the green and blue channels are very weak ! Red is much stronger. But the green and blue channel are just enough illuminated it seams. the histogram peaks are fully visible in the histogram. Notice in the screenshot the preivew fitler slider settings to show the flat. DDP is off, and I manipulated the white value and gamma value.
In the statistics, you’ll also see RGB calirbation values, these are just to properly do flat calibration without upsetting the color balance in the original light frames. In APP, the flat calibration won’t affect the RGB ratios of your lights frames, unlike other programs where flat calibrated lights suddenly will have a totally different color.
