(Fwd) Spectral Question
Guest wrote on Aug 31, 2006
Hello IRAF:
A question about wavelength scaling of a echelle star spectrum 'xyz'. I have
identified all the thorium comparison lines in 'thxyz' with IDENTIFY and
legendre order 6, and these identifications have gone into 'database/idthxyz'.
Then, after linking the two with REFSPEC, I use DISPCOR to produce a
linearized star spectrum 'xyz.wv'. Then I can plot 'xyz.wv' with SPLOT.
The 'xyz.wv' header gives for each order a number which may be the wavelength
of pixel zero, a number which is about the dispersion in angstroms per pixel,
and another number of the order of E-05 which I don't know how to use, but
I suppose takes account of the non-linearity of 'xyz'. I presume there
is a simple expression, using these parameters, connecting pixel number
with wavelength.
My question: is there such an expression that can be used to produce a list
of counts vs. wavelength?
If I had used some other polynomial or a spline in IDENTIFY, would
the numbers in the image header change?
The reason for all this is that I have sent the fits file of a reduced
spectrum to someone who has no access to IRAF or SPLOT.
Thank you.
George Herbig
Post generated using Mail2Forum (http://www.mail2forum.com)
A question about wavelength scaling of a echelle star spectrum 'xyz'. I have
identified all the thorium comparison lines in 'thxyz' with IDENTIFY and
legendre order 6, and these identifications have gone into 'database/idthxyz'.
Then, after linking the two with REFSPEC, I use DISPCOR to produce a
linearized star spectrum 'xyz.wv'. Then I can plot 'xyz.wv' with SPLOT.
The 'xyz.wv' header gives for each order a number which may be the wavelength
of pixel zero, a number which is about the dispersion in angstroms per pixel,
and another number of the order of E-05 which I don't know how to use, but
I suppose takes account of the non-linearity of 'xyz'. I presume there
is a simple expression, using these parameters, connecting pixel number
with wavelength.
My question: is there such an expression that can be used to produce a list
of counts vs. wavelength?
If I had used some other polynomial or a spline in IDENTIFY, would
the numbers in the image header change?
The reason for all this is that I have sent the fits file of a reduced
spectrum to someone who has no access to IRAF or SPLOT.
Thank you.
George Herbig
Post generated using Mail2Forum (http://www.mail2forum.com)
Mike Fitzpatrick wrote on Aug 31, 2006
See the WSPECTEXT task in ONEDSPEC, use SCOPY to copy an echelle order to a 1-D spectrum. I could comment more on the various numbers you mention if you said what keywords they were.
-Mike
-Mike
Last post on Aug 31, 2006