FITS file doubles in size after preprocessing

Image processing, astrometry, photometry, etc.
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fabdev
Posts: 461
Joined: 03 Dec 2018, 21:43

Re: FITS file doubles in size after preprocessing

Post by fabdev » 17 May 2019, 10:57

OK, the range is 437..68691 (it can be read on the status bar of the image too), so it exceeds the 16 bit range.

The cause is the flat field correction. This can happen if the bias of the camera is low and the vignetting is strong.

To force a 16 bit range before saving there are several ways, for example the command: Arithmetic / Clamp / Maximum.

For a scientifically correct result the flat field must also be corrected from its dark frame.

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Rudi
Posts: 152
Joined: 08 Jan 2019, 04:47

Re: FITS file doubles in size after preprocessing

Post by Rudi » 17 May 2019, 13:44

Ok Fabio. I will use dark flats next time.
I was also recommended doing that for my new camera on a danish Astro site.
/Rudi

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