Help me understand synthetic bias

Software Siril
1

im using siril 1.2.0. to preface, im an absolute noob, im new to all this and trying to figure out the script stuff is all greek to me.

Im trying to fix my flats over correcting. I saw that using a synthetic bias will help me fix my issue. I somehow managed to figure out that i can edit the default script. I tried editing the default script, got rid of the bias stacking part and tried to paste

calibrate flat -bias=“=256”
calibrate flat -bias=“=10*$OFFSET”

in the flat calibration section instead of calling the master bias thingy
then I get this error

1:35:51: .[any_allowed_extension] not found.
01:35:51: Error in line 31 (‘calibrate’): invalid arguments.
01:35:51: Exiting batch processing.
01:35:51: Setting CWD (Current Working Directory) to ‘F:\Astrophotography\Camera Dump\Siril testy flats’
01:35:51: Script execution failed.
01:36:51: Reading FITS: file result_36s.fit, 3 layer(s), 5202x3464 pixels, 32 bits

i reread the article and it says “The second expression needs as well that your imaging software writes a key OFFSET or BLKLEVEL in the FITS headers to log the offset setting. The level must be given in ADU (not float, even if you are working in 32b).”

and that takes me to path parsing, idk if im in the right direction but trying to read on how to write a key in the fits header is making no sense to me. im basically at my limit. none of those words are in the bible​:sob::sob:. i have no coding knowledge so if someone can teach it to me like im a kid, that would be nice or better share a script where i can adjust the offset with note pad

i looked around and someone did mention to do the same what i did, but in my case i get an error.

2

forgot to ad, i think i also figured to use the stuff on the top of the article with convert offset and probably using that info. still i have no clue how it works, the coding stuff. Im using a DSLR canon t3i btw

3

Hello and welcome.

Please, could you paste the modified script you use (please, use the preformatted text marker)

4 


requires 1.2.0


# Convert Flat Frames to .fit files
cd flats
convert flat -out=../process
cd ../process

# Calibrate Flat Frames
calibrate flat -bias="=256"
calibrate flat -bias="=10*$OFFSET"

# Stack Flat Frames to pp_flat_stacked.fit
stack pp_flat rej 3 3 -norm=mul -out=../masters/pp_flat_stacked
cd ..

# Convert Dark Frames to .fit files
cd darks
convert dark -out=../process
cd ../process

# Stack Dark Frames to dark_stacked.fit
stack dark rej 3 3 -nonorm -out=../masters/dark_stacked
cd ..

# Convert Light Frames to .fit files
cd lights
convert light -out=../process
cd ../process

# Calibrate Light Frames
calibrate light -dark=../masters/dark_stacked -flat=../masters/pp_flat_stacked -cc=dark -cfa -equalize_cfa -debayer

# Align lights
register pp_light

# Stack calibrated lights to result.fit
stack r_pp_light rej 3 3 -norm=addscale -output_norm -rgb_equal -out=result

# flip if required
load result
mirrorx -bottomup
save ../result_$LIVETIME:%d$s

cd ..
close
5

This is nonsense. The flat must be calibrated once. The first line is enough. BUT you must evaluate the value of your setup as explained here because you have a DSLR.

6

ok thanks, I thought you needed both of those lines for this to work. ok this makes it more easier. thanks for the help