procras le août 07, 2018, 03:05:08 15
Many thanks for the updated Siril.

I look forward to scripted pre-processing

Here is a sample

Camera   - Zwo  ASI1600MM-Cooled
Filters  - RGB and IR cut (as luminosity)
OTA      - Skywatcher 80ED
Mount    - AZ EQ6-GT
Software - Indi/Ekos, Rasberry PI running indi on scope, Kstars on PC in house.

Lights 20 sec exposures R G B L (10 of each), camera cooled to -10 degrees C
Bias (20 exposures)
Dark (20 exposures)
Flat R G B L (20 of each)

Used Siril to preprocess, register and stack the lights.

Stack Master Bias

Preprocess Darks to subtract offset/bias
Stack Darks to make Master Dark

Stack Flat R G B L to make MasterFlat-R|G|B|L

Preprocess Lights RGBL Using MasterDark and MasterFlat-R|G|B|L
Register the preprocessed Lights
Stack the registered preprocessed Lights

I then aligned the Stacked Lights so that all the R B B L were registered with each other.

I then used image processing to do the RGB composition after strecting with asinh.

Finally exported as png to gimp to touch up and reduce the size of the image.


lock042 le août 09, 2018, 11:04:05 11

Thank you for your feedback. Take a llook to darktable in order to remove chromatic aberration in your finale image if you want.
Good job.


procras le août 09, 2018, 01:19:29 13
Thanks for looking at the image.

I tried Darktable but it only wants raw files for the chromatic abbertion tool, I am exporting the composite as png.

Gimp 2.10 has a script fix-ca which appears to shift the colours left, right, up, down so won't fix my
colour fringes. Or at least I couldnt get it to work the correct way.

The appearance of the chromatic aberration is probably mostly due to the processing rather than my lens.
The fringes are all around the stars and occur in different colours.

There is a nice warning on the dialog when you select Image Processing->RGB Compositing
This says

WARNING: You should not perform a LRBG combination with linear images. Process images before.

So I stretched the L R B G images before combining them to make the final LRGB composite.

I am not sure what the best method of stretching should be, as it probably has to be applied
similarly to all of the frames L R G B, used in the final composited image.

I used the Histogram transformation tool (eg. Autostretch by clicking the cogs, also tried dragging the midtones slider) on one frame, eg R_stacked.fits and then jotted down the Midtones: and Shadows: settings.

I saved this frame as R_stretched.fits

And then applied the same values for Midtones: and Shadows: for the other frames needed for the composite image
- G_stacked.fits
- B_stacked.fits
- L_stacked.fits
and saved them accordingly as;
- G_stretched.fits
- B_stretched.fits
- L_stretched.fits

Then I loaded these stretched images into the RGB Compositing tool Image Processing->RGB Compositing and went from there.

I tried to follow the documentation as best I could.
What method's do others use?

P.S. I looked at the lights and stacked frames and the red channel is a bit out of focus  :(
« Modifié: août 09, 2018, 08:42:55 20 par procras »