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 The automatic dispersion range for spectra follows with the following steps :
- Search by UCDs or UTYPEs :
| ucd |
em.wl;stat.min(max) |
| utype |
sed:SpectralMinimum(Maximum)Wavelength |
The first keyword(s) matching any of these conditions is taken as dispersion range
- Search by WCS keywords : If the previous search fails, the loader try to find something in WCS keywords (see NOAO page)
CUNIT# or TCUNI# |
Dispersion unit |
CTYPE# or TCTYP# |
Dispersion type |
CRVAL# or TCRVL# |
Reference value |
CDELT# or TCDLT# |
Dispersion per pixel |
NAXIS# |
Number of pixels |
If all WCS keywords (# is the axis number) are present, the spectal range can be set.
- Search by columns : If there is no valid WCS keyword set, the data loader tries to find out a column looking like a spectral dispersion. Below id the regular expression used in this context :
(?i)((channel)|(wavelength)|(freq)|(frequency)) |
last update 2008-05-13
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Automatic Detection of Spectral Range.
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