Kevin
Which DSO is this?
Looking in the ZWO User Group, the debayer pattern for an ASI1600MC-cool is GRBG but keep this in mind
http://www.zwoug.org/viewtopic.php?f=21&t=6480. If Flip is used, then the debayer pattern gets changed.
There seems to be active debate in astro forums about which is the correct debayer patter for the ASI1600MC-Cool, with the ZWO owner suggesting GRBG (and he should know). Perhaps unwittingly, 'image flip' has played a part.
For the images in this discussion, colour space was RAW8, Output was FITS and Flip was None (see the settings file above). Because the images were captured as RAW8 the resultant 8-bit FITS files were unable to be debayered in Deep Sky Stacker (DSS will debayer 16-bit FITS). The result was a monochrome image with a check pattern overlay.
This is debayered as GRBG, stacked in Deep Sky Stacker with green adjustment applied, black point set and curve stretched in GIMP and cropped to show only the significant feature on the image. Not bad for a quick and dirty post-process but YMMV
- GRBG-final.PNG (121.25 KiB) Viewed 4414 times
A sample of 5 captures were debayered in PIPP and the resultant FITS files stacked in DSS, resulting in a coloured image with no check overlay. Minimal post processing was carried out in GIMP. No attempt was made to adjust colour. All 4 debayer patterns were used in PIPP. These are the outcomes (cropped to show the main feature of the image, as the output images are 70Mb and 4000x2000 pixels).
- GBRG.PNG (44.68 KiB) Viewed 4414 times
- BGGR.PNG (46.66 KiB) Viewed 4414 times
- RGGB.PNG (53.37 KiB) Viewed 4414 times
- GRBG.PNG (33.69 KiB) Viewed 4414 times
Below is a brief description of the process followed. If there is enough interest, I can work this up into a HOWTO document which would be more helpful to those starting out with all this (such as me!)
This is one of the original capture files opened in FITS Liberator. Note the 8-bit and the check pattern. Also the histogram is a 'good' shape for a DSO - offset from the LHS (no loss of data) and tailing off to the RHS (minimal over-exposed pixels).
- RAW8-FITS.png (39.57 KiB) Viewed 4413 times
The 5 files were loaded into PIPP. On the 'Input Options' tab, 'Debayer Monochrome Frames' was selected and 'GBRG' was selected. On the 'Output Options' tab, FITS was selected as the output format. On the 'Do Processing' tab, 'Start' was clicked.
A PIPP processed file opened in FITS Liberator looks like this. Check pattern now gone, whether or not the colours are right is another issue.
- debayered-FITS.PNG (66.71 KiB) Viewed 4414 times
The 5 PIPP output FITS files were loaded into Deep Sky Stacker and processed. These were the DSS settings used:
- DSS-settings.PNG (12.18 KiB) Viewed 4414 times
The DSS output looked like this. The Green is slightly out of alignment but can be adjusted by the slider. A file called Autosave.tif was created.
- DSS-output2.PNG (26.07 KiB) Viewed 4414 times
The autosave.tif file was loaded into GIMP. Using Colors > Curves, the black point was set and a stretch applied. The processed image was exported as a PNG.
- GIMP-before.PNG (23.03 KiB) Viewed 4414 times
- GIMP-adjust-black-point-and-stretch.PNG (28.23 KiB) Viewed 4414 times
Due to file sizes, the output was cropped and colours reduced using FastStone Image Viewer.
The above process was repeated using debayer patterns of GBRG, BGGR, RGGB, GRBG, in order to see which is the best result.
The sizes of some files created during the above process:
- Original FITS capture 16Mb
- TIF output from DSS 150Mb
- Working copy in GIMP 600Mb
- Exported PNG from GIMP 70Mb
Software used:
- GIMP v2.9.5 (will process 16-bit TIF without data loss)
- FastStone Image Viewer v6.3
Deep Sky Stacker and the debayering of 16 bit FITS files. From the menu
- DSS-options.PNG (4.67 KiB) Viewed 4414 times
select the checkbox and choose a debayer pattern from the dropdown
- DSS-debayer-16-bit-FITS.PNG (19.97 KiB) Viewed 4414 times
For completeness, the PIPP output was tested with FITS, PNG and TIF. All 3 output types were able to be stacked in DSS.