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FITS keywords for pixel size of CCD

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FITS keywords for pixel size of CCD was created by Phil Shepherd

I have been chatting to Peter from CloudMakers as I have been using his Atik CCD driver in my INDI setup on an oDroid.

I managed a proper run with it all on Monday night & have only just started to look in detail at the test images I took.

I am use to Pinpoint when solving FITS images & have used Maxim in the past - both of these use XPIXSZ & YPIXSZ for the pixel size. This has allowed the focal length to be calculated along with the solve. INDI uses PIXSIZE1 & PIXSIZE2

What I also notice is happening is, when I binned the image x4, the PIXSIZE1 & 2 remain at 6um's which I presume is normal, and XBINNING/YBINNING is 4...

Problem is, none of my external programs use PIXSIZE1 & 2.

I realise that the FITS "standard" is almost anything but a standard with all the extensions, but would like to get clarity here about this.

For me, XPIXSZ & YPIXSZ would show the "logical" size.... i.e. x1 binning = 6um, x4 binning = 24um, etc... This would be consistent with at least some of the other programs I use.

Phil
5 years 5 months ago #30844

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Replied by Phil Shepherd on topic FITS keywords for pixel size of CCD

As a quick follow-up, this is the fudge I made on my setup :

file : libindi/libs/indibase/indiccd.cpp
// XPIXSZ and YPIXSZ are logical sizes including the binning factor
    double xpixsz = pixSize1 * targetChip->getBinX();
    double ypixsz = pixSize2 * targetChip->getBinY();
    fits_update_key_dbl(fptr, "XPIXSZ", xpixsz, 6, "physical X dimension of the sensor's pixels in microns. Includes binning", &status);
    fits_update_key_dbl(fptr, "YPIXSZ", ypixsz, 6, "physical Y dimension of the sensor's pixels in microns. Includes binning", &status);

Phil
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5 years 5 months ago #30846

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Replied by Eric on topic Re:FITS keywords for pixel size of CCD

Sounds a good implementation to me. That could certainly be added to the FITS generator of the CCD driver. You should file a PR on github with your code.

-Eric
5 years 5 months ago #30876

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Replied by Jasem Mutlaq on topic Re:FITS keywords for pixel size of CCD

What other programs use XPIXSZ & YPIXSZ in the same meaning as you defined?
5 years 5 months ago #30879

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Replied by Phil Shepherd on topic Re:FITS keywords for pixel size of CCD

Pinpoint, MaxPoint & MaximDL (in the past)

I found Maxim has documented the FITS keywords it uses, for example
diffractionlimited.com/help/maximdl/FITS...ader_Definitions.htm

Edit:
I'm not sure now that Pinpoint uses XPIXSZ & YPIXSZ...
Last edit: 5 years 5 months ago by Phil Shepherd.
5 years 5 months ago #30884

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Replied by Jasem Mutlaq on topic Re:FITS keywords for pixel size of CCD

Ok, please submit a PR. The comment is too long. Just make it "X binned pixel size in microns" and "Y binned pixel size in microns"
5 years 5 months ago #30888

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Replied by Phil Shepherd on topic Re:FITS keywords for pixel size of CCD

k.. I'll get it down when I have a few minutes at the weekend..

Phil
5 years 5 months ago #30903

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Replied by Paul on topic Re:FITS keywords for pixel size of CCD

Extract of Nebulosity FITS file
CREATOR = 'Nebulosity v4.0.4' / program and version that created this file
INSTRUME= 'QSI 583ws S/N 00504126' / instrument name
DATE = '2015-12-29T12:09:04' / UTC date that FITS file was created
DATE-OBS= '2015-12-29T11:58:46' / YYYY-MM-DDThh:mm:ss observation start, UT
XPIXSZ = 5.4 / X pixel size microns
YPIXSZ = 5.4 / Y pixel size microns
CCD-TEMP= -15. / CCD temp in C
5 years 5 months ago #30904

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Replied by Phil Shepherd on topic Re:FITS keywords for pixel size of CCD

aha.. another one..
5 years 5 months ago #30906

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Replied by Phil Shepherd on topic Re:FITS keywords for pixel size of CCD


OK.. I think I have done it correctly - 1st time I've ever done it...

Please check & let me know

Phil
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5 years 5 months ago #30915

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Replied by Phil Shepherd on topic Re:FITS keywords for pixel size of CCD

FYI,

I just found that PixInsight's plate solve routine puts in XPIXSZ & YPIXSZ upon a successful solve

Phil
5 years 5 months ago #30931

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