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I am trying to subtract telluric lines from a CRIRES spectrum (high res, K-band spectra).
Both the fast rotator and the object spectra look fine when plotted, and have no problem being fed to various tasks (e.g. fxcor, specplot, splot, scopy etc).
However, when I do telluric I get the following message:Warning: Calibration spectrum negative or zero (set threshold parameter)Now, not only the calibration spectra are just fine( not negative and not zero) , but changing the threshold parameter (even by a lot!) does not make any difference.Any idea?Thanks!Sara

See threads such as https://iraf.net/phpBB2/viewtopic.php?t=81566&highlight=telluric+negative+zero
This should be fixed in v2.14, but it may also be there is another case that hasn't been corrected. Basically, a missing keyword is causing a cascade of errors and due to a bug the wrong error message is being printed. So, your calibration image may be fine, but a missing keyword in your input image is the real problem.-Mike

Thanks. Any idea which one is the missing keyword?
It is not extver (I tried). It seems pretty confusing and I am stuck.Sara

I'm not sure: AIRMASS, DC-FLAG, CRVAL/CRPIX ??? Post an image header and I'll see if I can spot anything obvious.-Mike

Hi Mike,I think I fixed it. Thanks!Sara

I have the same problem with the TELLURIC function -- I get the message "Warning: Calibration spectrum negative or zero (set threshold parameter)" no matter what value I set the "threshold" keyword parameter to.The header of my target image is the following (calibration/standard star header is of the same format). Are any keywords missing? What might be the problem?-- IanSIMPLE = T / Fits standard
BITPIX = -32 / Bits per pixel
NAXIS = 3 / Number of axes
NAXIS1 = 1024 / Axis length
NAXIS2 = 6 / Axis length
NAXIS3 = 4 / Axis length
EXTEND = F / File may contain extensions
ORIGIN = 'NOAO-IRAF FITS Image Kernel July 2003' / FITS file origina
r DATE = '2008-07-22T22:29:40' / Date FITS file was generated
IRAF-TLM= '16:29:43 (22/07/2008)' / Time of last modification
TELESCOP= 'Keck II ' / Telescope
OBSERVER= 'Keck Engineering ' / Observer
OBJECT = ' 55 Cancri' / Object name
COMMENT = 'Obs # 1 ' / Comment
ROOTNAME= 'mar21s ' / File Root Name
FILENUM = 128 / Frame Number
FILENAME= 'mar21s0128.fits ' / Name of file
OUTDIR = '/sdata602/nirspec/2008mar21/spec/ ' / Data Directory
SCRIPTNA= 's20Mar0027.csh ' / Name of current script
FILNAME = 'NIRSPEC-7 ' / Filter Name
SLITNAME= '0.720x24 ' / Slit Name
SLITPA = 118.720 / Slit position angle
SLITX = 131.000 / X pixel of the center of the slit
SLITY = 125.500 / Y pixel of the center of the slit
SLITANG = 13.600 / Slit angle in the scam. CCW from hor
SCAMPA = 195.120 / Scam position angle
ITIME = 3.000 / Integration time per coadd
COADDS = 20 / Number of coadds
SAMPMODE= 2 / 1=Single; 2=CDS; 3=MCDS
DETBIAS = 450 / Detector bias setting (0-4096)
MULTISPE= 16 / Number of multiple reads
SAMPRATE= 250 / Spec sampling rate in KHz
Q1OFFSET= 3240 / Aladdin Quadrant 1 preamp offset
Q2OFFSET= 3240 / Aladdin Quadrant 2 preamp offset
Q3OFFSET= 3240 / Aladdin Quadrant 3 preamp offset
Q4OFFSET= 3240 / Aladdin Quadrant 4 preamp offset
GAIN.SPE= 4 / Preamp gain setting 1-4
FREQ.SPE= 4 / Preamp filtering frequency setting 1
CRYOTEMP= 30.200 / Aladdin cold head temperature
FIL1POS = 11 / Filter 1 Position
FIL2POS = 18 / Filter 2 Position
SLITPOS = 8 / Slit Position
ECHLPOS = 62.220 / Echelle position
DISPPOS = 35.660 / Cross Disperser position
IROTLOC = 54294 / Step position of Image rotator
CALMPOS = 0 / Cal. Mirror Position, 0=out, 1=in
CALCPOS = 0 / Cal. Cover Position, 0=out, 1=in
CALPPOS = 0 / Cal. Pinhole Position, 0=out, 1=in
NEON = 0 / Neon lamp: 1=on, 0=off
ARGON = 0 / Argon lamp: 1=on, 0=off
KRYPTON = 0 / Krypton lamp: 1=on, 0=off
XENON = 0 / Xenon lamp: 1=on, 0=off
ETALON = 0 / Etalon lamp: 1=on, 0=off
FLAT = 0 / Flat lamp: 1=on, 0=off
UTC = '08:14:23.01 ' / coordinated universal time (h)
AIRMASS = 1.03676 / air mass (1.04)
AXESTAT = 'tracking ' / axes control status
AZ = -53.92620 / telescope azimuth (-53.93 deg)
CALOCAL = 0.01264 / collimation azimuth local (45.
CELOCAL = -0.01027 / collimation elevation local (-
CURRINST= 'NIRSPEC ' / current instrument
DATE-OBS= '2008-03-21 ' / universal date of observation
DCSSTAT = 'standby ' / drive and control status
DCSVERS = '6-3-0 ' / drive and control version
DEC = 28.33225 / telescope declination (+28:19:
DOMEPOSN= 306.18000 / dome azimuth (306.18 deg)
DOMESTAT= 'tracking ' / dome status
EL = 74.68381 / telescope elevation (74.68 deg
EQUINOX = 2000.00000 / telescope equinox (2000.0)
FOCALSTN= 'rnas (right nasmyt' / focal station
HA = 14.06607 / telescope hour angle (+00:56:1
LST = '09:49:22.48 ' / local apparent sidereal time (
MJD-OBS = 54546.34332 / modified julian date of observ
PARANG = 120.33286 / parallactic angle astrometric
PARANTEL= 120.28237 / parallactic angle telescope (1
PONAME = 'REF ' / pointing origin name
POXOFF = 0.00000 / pointing origin x offset (0.00
POYOFF = 0.00000 / pointing origin y offset (0.00
POXPOS = 0.00066 / pointing origin xposition (0.6
POYPOS = 0.00121 / pointing origin yposition (1.2
PONAME1 = 'REF ' / pointing origin name 1
POXPOS1 = 0.00066 / pointing origin xposition 1 (0
POYPOS1 = 0.00121 / pointing origin yposition 1 (1
PONAME2 = 'SLIT ' / pointing origin name 2
POXPOS2 = 0.00096 / pointing origin xposition 2 (0
POYPOS2 = 0.00064 / pointing origin yposition 2 (0
PONAME3 = 'REFA ' / pointing origin name 3
POXPOS3 = -0.00406 / pointing origin xposition 3 (-
POYPOS3 = 0.05239 / pointing origin yposition 3 (5
PONAME4 = 'DREF ' / pointing origin name 4
POXPOS4 = 0.00039 / pointing origin xposition 4 (0
POYPOS4 = -0.00090 / pointing origin yposition 4 (-
PONAME5 = 'DREFA ' / pointing origin name 5
POXPOS5 = -0.00057 / pointing origin xposition 5 (-
POYPOS5 = -0.05447 / pointing origin yposition 5 (-
PONAME6 = 'HNOD1 ' / pointing origin name 6
POXPOS6 = 0.00342 / pointing origin xposition 6 (3
POYPOS6 = 0.00057 / pointing origin yposition 6 (0
PONAME7 = 'HNOD2 ' / pointing origin name 7
POXPOS7 = -0.00318 / pointing origin xposition 7 (-
POYPOS7 = -0.00113 / pointing origin yposition 7 (-
PONAME8 = 'LNOD1 ' / pointing origin name 8
POXPOS8 = -0.00005 / pointing origin xposition 8 (-
POYPOS8 = 0.00536 / pointing origin yposition 8 (5
PONAME9 = 'LNOD2 ' / pointing origin name 9
RA = 133.14653 / telescope right ascension (08:
ROTCALAN= 0.00000 / rotator calibration angle (0.0
ROTMODE = 'stationary ' / rotator tracking mode
ROTPPOSN= 0.00000 / rotator physical position (0.0
ROTPOSN = -0.00000 / rotator user position (-0.00 d
ROTREFAN= 0.00000 / rotator reference angle (0.00
SECFOCUS= 0.00186 / secondary mirror focus raw (1.
SECTHETX= -0.00005 / secondary mirror thetax (-9.8
SECTHETY= -0.00102 / secondary mirror thetay (-210.
TARGDEC = 28.33082 / target declination (+28:19:50.
TARGEPOC= 2000.00000 / target epoch (2000.000000)
TARGEQUI= 2000.00000 / target equinox (2000.000000)
TARGFRAM= 'FK5 ' / target frame
TARGNAME= '55 Cnc ' / target name
TARGPLAX= 0.00000 / target parallax (0.0 arcsec)
TARGPMDC= 0.00000 / target proper motion dec (0.00
TARGPMRA= 0.00000 / target proper motion ra (0.000
TARGRA = 133.14917 / target right ascension (08:52:
TARGRADV= 0.00000 / target radial velocity (0.0000
TELESCOP= 'Keck II ' / telescope name
TELFOCUS= 0.00126 / telescope focus compensated (1
TUBETEMP= -3.25567 / tube temperature (-3.26 degC)
UTC = '08:14:23.01 ' / coordinated universal time (h)
EXPTIME = '60.0 '
WCSDIM = 3
LTM1_1 = 1.
LTM2_2 = 1.
WAT0_001= 'system=equispec'
WAT1_001= 'wtype=linear label=Pixel'
WAT2_001= 'wtype=linear'
FIXPIX = 'Jul 22 16:26 Bad pixel file is /Users/ianc/proj/pcsa/data/
oc/55cnc'FLATCOR = 'Jul 22 16:26 Flat field image is /Users/ianc/proj/pcsa/dat
proc/55c'CCDSEC = '[1:1024,1:1024]'
CCDMEAN = 2321.822
CCDMEANT= 901211180
CCDPROC = 'Jul 22 16:26 CCD processing done'
BANDID1 = 'spectrum - background fit, weights variance, clean yes'
BANDID2 = 'raw - background fit, weights none, clean no'
BANDID3 = 'background - background fit'
BANDID4 = 'sigma - background fit, weights variance, clean yes'
APNUM1 = '1 1 73.84 80.98'
APNUM2 = '2 2 210.25 217.56'
APNUM3 = '3 3 353.63 361.13'
APNUM4 = '4 4 505.13 512.71'
APNUM5 = '5 5 665.82 673.23'
APNUM6 = '6 6 837.29 844.29'
CTYPE1 = 'PIXEL '
CTYPE2 = 'LINEAR '
CTYPE3 = 'LINEAR '
CRVAL1 = 1.
CRPIX1 = 1.
CD1_1 = 1.
CD2_2 = 1.
CD3_3 = 1.
LTM3_3 = 1.
WAT3_001= 'wtype=linear'
REFSPEC1= 'mar21s0128s'

Bump... does anyone out there have any ideas for this?

Hi,My attempt to reproduce this with your header did not result in a problem. You could send me (valdes@noao.edu) the spectrum, calibration, and parameters if you want.One suggestion is to use imreplace or imfunction to explicitly set all values in teh calibration to positive values; e.g.[code:1:d454d3eb13]
imreplace calspec 0.1 lower=0.1
[/code:1:d454d3eb13]The actual value depends on the flux scale of the data.Yours,
Frank Valdes