Example for assigning new values to FITS Headers?

[JuergenTerpe]

Hi,

I'm trying to assign new values with a custom keyword to the FITS headers and it seems I'm doing it wrong, obviously (despite it seems to be intuitive). Do you have a working example how to do so? Here is my code, perhaps you can see immediately what I'm doing wrong?

       if let fits = try? FitsFile.read(contentsOf: image.url) {
		let header = fits.prime.headerUnit
		
		if settings.hfr, let hfr = image.hfr {
			header["HFR"] = hfr
		}
		
		if settings.fwhm, let fwhm = image.fwhm {
			header["FWHM"] = fwhm
		}
		
		if settings.eccentricity, let ecc = image.eccentricity {
			header["ECCEN"] = ecc
		}
		
		if settings.mean, let mean = image.mean {
			header["MEAN"] = mean
		}
		
		if settings.median, let median = image.median {
			header["MEDIAN"] = median
		}
		
		if settings.aduMin, let aduMin = image.aduMin {
			header["ADUMIN"] = aduMin
		}
		
		if settings.aduMax, let aduMax = image.aduMax {
			header["ADUMAX"] = aduMax
		}
		
		if settings.numStars, let numStars = image.numStars {
			header["NSTARS"] = numStars
		}
		
		if settings.rms, let rms = image.rms {
			header["RMS"] = rms
		}
		
		if settings.rmsRA, let rmsRA = image.rmsRA {
			header["RMSRA"] = rmsRA
		}
		
		if settings.rmsDEC, let rmsDEC = image.rmsDEC {
			header["RMSDEC"] = rmsDEC
		}
		
		if let pathURL = settings.path {
			let url = pathURL.appendingPathComponent(image.FileName)
			fits.write(to: url) { error in
				print(error.localizedDescription)
			} onCompleation: {
				onProgress()
			}
		} else {
			fits.write(to: image.url) { error in
				print(error.localizedDescription)
			} onCompleation: {
				onProgress()
			}
		}
	}

The FITS file will be written successfully, but PixInsight cannot open it - and also not FITScore. PixeInsight gives me this error message:

*** Error: PCL Legacy FITS Format Support: Unable to open FITS file: /Volumes/ImageStore/Leo Triplett/Temp/LIGHT/2024-04-11_00-33-12_Baader Neodymium_-4.90_180.00s_0035.fits
CFITSIO error message stack:
01 : Character 9 in this keyword is illegal. Hex Value = FFFFFF80
02 : �Ä�Ú�Ä�Ý�Ç�æ�Ê�ç�½�é�Å���¼�õ�¿�è�À�ô�Ê�æ�»�ó�¿�ð�¿�ë�Á�î�Ç�ò�¼�ñ�Â�ä�Á�ò�Ä
03 : Name of keyword no. 109 contains illegal character(s): �Ä�Ú�Ä�Ý�Ç�æ�Ê�ç�½�é�Å���
04 : Failed to read the required primary array header keywords.
05 : ffopen could not interpret primary array header of file:
06 : /Volumes/ImageStore/Leo Triplett/Temp/LIGHT/2024-04-11_00-33-12_Baader Neodymium
07 : -4.90_180.00s_0035.fits
*** Unable to open file: /Volumes/ImageStore/Leo Triplett/Temp/LIGHT/2024-04-11_00-33-12_Baader Neodymium-4.90_180.00s_0035.fits
<* failed *>

Thanks in advance for your help!

[JuergenTerpe]

I also tried this with strings.... Maybe, all this is not the intention how to use it.

[brampf]

Hi there!
haven't been working on this code for quite a while, so this might take a while. Can you share the file you are working on before and after you made your changes so I can have a look at it?

[JuergenTerpe]

Sure, I can do.

Some background information: I' writing an analysis tool to evaluate complete imaging sessions captured with NINA. There is an additional plugin available, which writes some important info into a csv file, such as HFR or star eccentricity. I wanted to provide an option to add this information into the FITS header for later use in PixInsight. This free and open source tool will use FitsCore.
This can be a very helpful tool for astrophotographers worldwide - at least for the Mac users.

I don't think your library is incorrect, I would think I don't do it right.

Regards and Thanks for having a look,
Jürgen

After Writing Header with new Data.fits.zip
Original.fits.zip