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Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:02
by Forum_2018
Hi,
Is it possible to setup AstroArt to save sequence images as camera RAW files, e.g. CR2 for Canon?
The fits files I get from AA6 sequences gived problems with other astronomy tools, PI / DSS.
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:04
by Forum_2018
The reason I ask, is also, that I am very much in doubt if I am using correct settings in AstroArt 6, when making image sequences. What a shame if I have wrong settings, and all images are ruined !!! ???
I am using the following settings:
When pre processing (stack), I use the following settings:
My camera is an unmodded Canon 1000D. The CCD cell bayer mask is:
RG
GB
as far as I can find out.
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:04
by Forum_2018
Hi,
the images downloaded from the camera are saved always as grayscale 16 bit FITS, and they are 100% identical to the CR2s.
1) The "RAW Images" options of Preferences do not apply, they ares used only for opening CR2s.
2) The "Demosaic" option does not apply too, it's used only in the command "RGB Demosaic" and in "Preprocessing".
The options seem correct, but before using them in Preprocessing you should verify them (once in a while) performing a RGB demosaic by hand, just opening a "raw" FITS file downloaded from the camera, then menu Color / RGB Demosaic.
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:04
by Forum_2018
By the way, as a general rule, you should disable the option "DCRAW demosaic on load", so that you can see the original RAW images of your test images (the ones taken without a software).
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:05
by Forum_2018
Thanks Fabio.
1) Does the “DCRAW demosaic on load” affect the pictures taken? Or only when loading?
2) You day that the FITS is 100% identical to CR2 - does that mean that I could write the data bytes from the fitsfile (excluding header data) to a file with *.CR2 extension and it would be a CR2 file? Or do You mean that the fits contains the same information as CR2, just in another format?
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:05
by Forum_2018
1) No. When you download an exposure (in RAW format) from the camera it's always grayscale + bayer pattern, this can be seen with the Canon camera control 1.20. That option is used only when manually opening a CR2.
By the way, I don't understand: are you taking those image with Astroart? If yes, point(1) is obvious, maybe you are downloading them in JPEG format?
2) Yes. 100% identical, obviously. The RAW data is the most important thing of an astronomical image.
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:05
by Forum_2018
Looking again at your screenshots, I can see a problem: enabling both "DCRAW demosaic on load" in Preprocessing and "RGB demosaic" in Preprocessing is equivalent to apply the demosaic two times. Astroart will ignore the second one, but those options should not be set anyway. I suggest to disable the first one. If you convert on load, then it's impossible to correct dark frames and/or hot pixels.
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:06
by Forum_2018
Fabio, I tried removing FITS header information (first 2880 bytes) and write the remaining bytes to a file, but it is not recognised as a CR2 Canon RAW file?
Code: Select all
static void Main(string[] args)
{
string fitsFile = @"C:\temp\Fits2CR2\M13-60s-001.fit";
string cr2File = @"C:\temp\Fits2CR2\M13-60s-001.CR2";
List<byte> fileBytes = File.ReadAllBytes(fitsFile).ToList();
fileBytes.RemoveRange(0, 2880); // remove FITS header
File.WriteAllBytes(cr2File, fileBytes.ToArray()); // write the remaining bytes as CR2 file
}
Re: Save camera RAW (CR2) vs FITS
Posted: 26 Dec 2018, 20:06
by Forum_2018
It's normal, the CR2 has its own header, and it's compressed.
