iraf.net

There is only one extension for a spectrum fits file got by iraf.
However there are four parts including primary, background...

Splot can display the spectrum with wavelength and flux.

I tried to read the data of the spectral fits file, but only get integral number-flux relationship.

There should be some keyword in the header of the fits and splot can distinguish it?

How does splot do it?

How to get wavelength-flux relationship conveniently?

The WSPECTEXT task can be used to dump the spectral values (if I understand what you want to do). If the data are in the 3-D multispec format then to access each of the individual bands you would use an image section when calling the task, e.g.

cl\$this->_split2($m[0]) wspectext spec.fits[*,*,2] ......

and the output should be the wavelength vs the value of whatever is in the band (flux, variance, sky, etc).

See also the SPECWCS and SCOPY help pages for details.

Thank you. That works.