Additional info:

* FITS viewer configuration:
- Limited resources mode OFF.
- Auto stretch OFF.
- Auto debayer ON.
- 3D Cube ON.
- Non linear histogram ON.

* Some tests with FITS viewer:
- Saved the native format image to FITS and loaded it in FITS viewer - and it's the same as FITS transferred file (dark image).
- GIMP and Siril shows normal image for both files.
- Changed the bit depth to 8 using gimp and opened with FITS viewer - now shows normal image.

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