File: pix2wl.hlp

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.help pix2wl Aug2008 rvsao
.ih
NAME
pix2wl -- Compute the wavelength at a given pixel in a spectrum
.ih
USAGE	
.nf
pix2wl spectrum pixel
.fi
.ih
PARAMETERS
.ls spectrum
Spectrum image file with dispersion function
.le
.ls specext = 0
Spectrum extension number in multiextension FITS image
.le
.ls specnum 0
Spectrum number in multispec image (order in echelle image)
.le
.ls specband 0
Spectrum band in multispec image
.le
.ls pixel INDEF
Pixel at specified wavelength (returned)
.le
.ls wavelength INDEF
Wavelength in Angstroms for pixel
.le
.ls pixform "%8.3f"
IRAF format for pixel output
.le
.ls waveform "%8.3f"
IRAF format for wavelength output
.le
.ls nsum = 1
Number of pixels to sum across dispersion
.le
.ls verbose no
If yes, print the pixel value
.le
.ls debug = no
If yes, print the file name, transformation, and wavelength per pixel
.le

.ih
DESCRIPTION
Compute the wavelength at a given pixel in a spectrum, saving the
value as the pix2wl.wavelength parameter.  If the pixel is zero, the
wavelength at the start of first pixel (=0.5) is saved as pix2wl.wavelength,
and the wavelength at the end of the last pixel (=npts+0.5) is saved as
pix2wl.wave2.  Otherwise, pix2wl.wave2=INDEF.  If verbose=yes, print the
wavelength of the pixel (or if the pixel is zero, the wavelengths of the
first and last pixels) using the pix2wl.waveform format.  If debug=yes,
print spectrum image name, followed by the wavelength value using the
pix2wl.waveform format, the pixel falue using the pix2wl.pixform format,
and the delta wavelength per pixel across this pixel.
.ih
EXAMPLES

1) Compute the wavelength at a given pixel for use in a CL script:
.nf
rvsao> pix2wl 22572.fits 3000   
rvsao> =pix2wl.wavelength
6435.7338761065
rvsao>
.fi

2) Print the wavelength at a given pixel:
.nf
rvsao> pix2wl 22572.fits 3000 v+
6435.734
rvsao>
.fi

3) Print the wavelength at a given pixel more verbosely:
.nf
rvsao> pix2wl 22572.fits 3000 d+
22572.fits: 3000 -> 6435.734 (0.5744/pix)
rvsao> 
.fi

4) Compute the wavelength range of an image for use in a CL script:
.nf
rvsao> pix2wl 22572.fits 0
rvsao> =pix2wl.wavelength
4712.8929877685
rvsao> =pix2wl.wave2
7065.5371880127
rvsao>
.fi

5) Print the wavelength range of an image:
.nf
rvsao> pix2wl 22572.fits 0 v+
4712.893 - 7065.537
rvsao>
.fi

6) Print the wavelength range of an image more verbosely:
.nf
rvsao> pix2wl 22572.fits 0 d+
22572.fits: 4712.893-7065.537 (4096 pixels, 0.5742/pix)
rvsao>
.fi

7) Check the inverse of the dispersion function:
.nf
rvsao> pix2wl 22572.fits 3000
rvsao> wl2pix 22572.fits pix2wl.wavelength v+
3000.000
rvsao>
.fi

.ih
AUTHOR
Doug Mink, Harvard-Smithsonian Center for Astrophysics

.endhelp