Fits Header integration time

Any plans to embed the integration time of completed files into the FITS header of future releases?


I thought it was already the case, if it’s not there, it’s a bug. Which stacking method and what kind of input files did you use?

Well i’ll be damned - you’re absolutely right! :rofl:

I don’t know how I failed to see it. :thinking:

In that case, please disregard.



Well, I couldn’t find that information either in the header of the result.FITS file.
To access the header I used : Image Information / FITS Header …
Please advice.

Hello Jean-Claude, don’t you have the EXPTIME keyword in the header of the stacked image?

Yes I have the EXPTIME keyword :
EXPTIME = 60. / Exposure time [s]
But this is the exposure time of a single image, not the TOTAL exposure time (integration time) of the stacked images

that’s strange. @lock042 if you have it running nearby can you check what happens to the total exposure on stacking result? From what I see in the code it’s only done when there is date information in the input files, but there is an exposure sum in that case.

EXPTIME should contain the sum of exposure.
But yes we need the date in the header because we compute a lot of interesting things in fact.

And generally, the date is written by default by every capture software.

Hi, I just checked that this has not been corrected in Siril 0.99.10 yet.

In my workflow it is.
Please share a header of stacking result

Screenshot 2021-06-15 at 20.22.36.pdf (694.1 KB)

Here is a stack of 27 x 30sec frames

What is your workflow.

Looks like the header of a single frame.

I use scripts that I adapted from the Siril scripts to fit the KStars output.
I’m attaching a script which doesn’t use any DOF.
Preproc_NoDBF.ssf (898 Bytes)

… but it’s the header of the stack !

When I use the standard script I have a right exptime.

This is not what I get.
Just to be sure that my modified scripts aren’t responsible for the wrong EXPTIME, I used the original script OSC_Preprocessing.ssf on a complete set of frames (lights, biases, darks, flats).
The lights directory contained 20 lights recorded with an EXPTIME = 10 sec
Thus the FITS Header of the result.fits should display : EXPTIME = 200 sec.
This is not the case as shown in the attached screenshot.
Screenshot 2021-06-16 at 08.39.58.pdf (641.7 KB)

Are you sure to reload the result.fits?

Yes I’m sure I reloaded the result.fits with Siril 0.99.10.
At the end of the process, I checked that the “EXPTIME bug” was found on other result.fits as you can see in the logs. The bug was always present.
Screenshot 2021-06-16 at 09.46.16.pdf (6.1 MB)
If you want to check yourself , I uploaded a few files at:
I preprocessed these files with the original OSC_Preprocessing.ssf script.

Applying standard script on your images I get:

SIMPLE  =                    T / file does conform to FITS standard
BITPIX  =                  -32 / number of bits per data pixel
NAXIS   =                    3 / number of data axes
NAXIS1  =                 4656 / length of data axis 1
NAXIS2  =                 3520 / length of data axis 2
NAXIS3  =                    3 / length of data axis 3
EXTEND  =                    T / FITS dataset may contain extensions
COMMENT   FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT   and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
BZERO   =                   0. / offset data range to that of unsigned short
BSCALE  =                   1. / default scaling factor
INSTRUME= 'ZWO CCD ASI1600MC-Cool' / instrument name
TELESCOP= 'Reducer '           / telescope used to acquire this image
OBSERVER= 'JCJ     '           / observer name
DATE    = '2021-06-16T08:53:58' / UTC date that FITS file was created
DATE-OBS= '2020-05-20T22:03:34.541000' / YYYY-MM-DDThh:mm:ss observation start,
EXPTIME =                  50. / Exposure time [s]
EXPSTART=     2458990.41914978 / Exposure start time (standard Julian date)
EXPEND  =     2458990.41982632 / Exposure end time (standard Julian date)
XPIXSZ  =                  3.8 / X pixel size microns
YPIXSZ  =                  3.8 / Y pixel size microns
XBINNING=                    1 / Camera binning mode
YBINNING=                    1 / Camera binning mode
FOCALLEN=                1960. / Camera focal length
CCD-TEMP=                 -15. / CCD temp in C
GAIN    =                  139 / Camera gain
OFFSET  =                   21 / Camera offset
CTYPE1  = 'RA---TAN'           / Coordinate type for the first axis
CTYPE2  = 'DEC--TAN'           / Coordinate type for the second axis
EQUINOX =                2000. / Equatorial equinox
OBJCTRA = '16 41 39.40'        / Image center R.A. (hms)
OBJCTDEC= '36 31 43.33'        / Image center declination (dms)
PROGRAM = 'Siril v0.99.11'     / Software that created this HDU

So, with 5 images, for me the behaviour is ok.