Fits Header integration time

Software Siril
1

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

Thanks

2

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?

3

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.

Thanks,

Mark

4

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.

5

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

6

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

7

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.

8

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.

9

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

10

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

11

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

12

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

Here is a stack of 27 x 30sec frames

13

What is your workflow.

Looks like the header of a single frame.

14

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)

15

… but it’s the header of the stack !

16

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

17

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)

18

Are you sure to reload the result.fits?

19

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: http://dl.free.fr/v8waw0evu
I preprocessed these files with the original OSC_Preprocessing.ssf script.

20

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.