Dark frames

[fuherb]

If my input image frames for stacking are DNG raw, but my dark calibration frame is FIT, will there be a mismatch so that dark calibration is not performed? I ask this because when I use Dark frames, the hot pixels seem to be still rather visible. If I use the build in hot pixel remover then the result is much better. I suppose the program will read the DNG and convert to FIT for processing. Is this the case?

[deufrai]

Hi

There should be no impact on Dark current subtraction, as long as the input format is handled by ALS. Even when data types are different (integers vs floating point, etc...) your master dark is processed to match your light's data format.

If you could provide some sample images (lights & master dark) we could have a look

[fuherb]

Some more updates on this issue.

I tried to redo a master dark again today. I took 20 dark subs and stacked them in Siril and made a FIT file. Using this FIT file as the dark subtraction file yields no effect. It ssems that ALS simply ignore it.

I then use Siril to convert just 1 DNG file into FIT and use this FIT as master. No effect.

I then try to simply rename these 2 FIT files as DNG. No effect.

I then realized I set Siril to work in 32 bits. So I redo everything in 16 bits to match the Light frames. No effect.

Last, I simply use 1 dark sub (DNG file) and use it as the dark subtraction file. It WORKS. Of course this is sub-optimal as this Dark Master is just 1 sub, no averaging of noise etc.

So it seems that if I use DNG file as Master Dark, ALS will recognize it. But FIT is not. The problem is I cannot find a way to stack a number of DNG into another DNG.

[fuherb]

A short summary with new info.

The camera I use is a Raspberry Pi HQ camera, and the images are captured in DNG format. I made more tests today and found more. I have been testing different combo:

DNG lights and FIT dark - not working DNG lights and DNG dark - work FIT lights and FIT dark - work FIT lights and DNG dark - not working

Apparently the same file type is required. But it might happen that the FIT format (converted from DNG using Siril) bear some different structure so it is not compatible with DNG?

[fuherb]

Sorry to post again within a short duration. Some good news.

After stacking 20 dark subs again in 16 bits, I got a FIT file. I then save this as a TIFF file. Using this tif file as the master dark in ALS I get things working. All hot pixels gone.

I don't know why but likely there are some compatibility issue. Anyhow it confirms that you do NOT need to have the same file type to get the dark subtraction work.

For the time being, I will use the tif file master as the solution.