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I am trying to work on REFSPEC. Using epar I input the reference spectrum and then run the task. It asks me for the input image which I promptly give it. It then gives me the following error: Image header parameter not found: (jd) First I thought that it was looking for Julian Date so I updated my reference header with the appropriate information. But I still get the same error. Why is this? Thanks, Rohit

Hello Rohit,In the default parameters REFSPEC wants to first sort the spectra by the numeric keyword JD. This is only a default and you would need to adjust parameters for your data. If you want more help send a listing of the parameters you are using (the output of lpar or dpar) and a header listing (the output of imhead spec l+).Yours,
Frank Valdes

Hello valdes, Sorry for the late reply. I was out observing. Here is what you asked for. Hope this helps! onedspec> lpar refspec
input = " " List of input spectra
answer = "yes" Accept assignment?
(references = "comb58_62.fits") List of reference spectra
(apertures = "") Input aperture selection list
(refaps = "") Reference aperture selection list
(ignoreaps = yes) Ignore input and reference apertures?
(select = "interp") Selection method for reference spectra
(sort = "jd") Sort key
(group = "ljd") Group key
(time = no) Is sort key a time?
(timewrap = 17.) Time wrap point for time sorting
(override = no) Override previous assignments?
(confirm = yes) Confirm reference spectrum assignments?
(assign = yes) Assign the reference spectra to the input spect
(logfiles = "STDOUT,logfile") List of logfiles
(verbose = no) Verbose log output?
(mode = "ql")
And here is the imhead of the spectrum file onedspec> imheader comb58_62.fits l+
comb58_62.fits[5858][real]:
No bad pixels, min=0., max=0. (old)
Line storage mode, physdim [5858], length of user area 1256 s.u.
Created Tue 19:04:33 10-Jun-2008, Last modified Mon 16:12:13 07-Jul-2008
Pixel file "comb58_62.fits" [ok]
EXTEND = F / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file originator
DATE = '2008-06-10T22:04:33' / Date FITS file was generated
IRAF-TLM= '16:12:13 (07/07/2008)' / Time of last modification
APNUM1 = '1 1 '
WCSDIM = 1
CTYPE1 = 'LINEAR '
CRVAL1 = 1.2205699682236
CRPIX1 = 1.
CDELT1 = 1.75875121056880E-5
CD1_1 = 1.75875121056880E-5
LTM1_1 = 1.
WAT0_001= 'system=equispec'
WAT1_001= 'wtype=linear label=Wavelength units=Angstroms'
DC-FLAG = 0
SFIT = '1 '
SFITB = '1 '
REFSPEC1= 'comb58_62'
NCOMBINE= 2

Since you have only one reference spectrum there is no need to do much to assign a reference spectrum to an object spectrum. You could use "select=match" in refspec or you could addhedit scispec refspec1 'comb58_62' add+That is, add a keyword REFSPEC1 to the science spectrum, scispec in the example, whose value is the reference spectrum file name.All the other choices for the refspec.select parameter depend on having a keyword in the header to sort against. The default is JD which is why you got the message. Your header doesn't really have any keyword that would be suitable for selecting a reference.Yours,
Frank Valdes