strange ISIS fault - displaying UVES Castor spectrum

[Robin Leadbeater]

If you display the UVES Castor spectrum from the ISIS database, then save it and compare this saved version with the spectrum displayed straight from the database, you see a large (non constant) wavelength shift between the two versions of the same spectra. (see attached) It does not happen with other UVES spectra in the database though. Does anyone else see the same fault?

What is happening ???
Any ideas ?
Robin

[Robin Leadbeater]

I think I understand what is happening. I had replaced the original UVES Castor spectrum in the ISIS database with one with a wider wavelength range that I had generated from the UVES POP website using the plot function there. The problem is that spectra produced using this function do not have equal bin widths across the wavelength range. ISIS plots these correctly but saves them incorrectly with equal bin widths.

Does anyone know how to generate files (fits or dat) with equal bin width from the UVES POP spectra ?

Many Thanks
Robin

[Peter Somogyi]

Hi Robin,

"Does anyone know how to generate files (fits or dat) with equal bin width from the UVES POP spectra ?"

I've already tried this feature in ISIS on .fit files with success:

resampling.png (9.94 KiB) Viewed 4500 times

"A/p" is matching with 'CRDELT1' value in the fits header. (However, never tried with .dat format.)

HTH
Peter

[Robin Leadbeater]

That works, thanks Peter !

That tool can convert a dat file with unequal bin sizes to an equal bin size fits file. That can then be converted to a dat file using the tool in the same ISIS window

Thanks again!
Robin

[Christian Buil]

Yes Peter is pointing the correct solution.

The UVES spectra variable sampling (presence of hole, ...) is always a problem.

Christian