[AstroPy] Reading in wavelength-calibrated spectra

Kevin Gullikson kevin.gullikson.signup@gmail....
Tue Aug 14 11:46:57 CDT 2012


Thanks for the quick replies, everyone. I guess I will take Kelle's
suggestion for now.

On Tue, Aug 14, 2012 at 10:54 AM, Andy Casey <acasey@mso.anu.edu.au> wrote:

> In the past I've done what Kelle has suggested (and I hope AstroPy will
> eventually be able to parse all of this, even if I end up writing it
> myself), but just for reference:
>
> http://iraf.net/irafdocs/specwcs.php
>
> Provides a good overview on the different dispersion representations that
> you'll typically find in FITS headers.
>
> Cheers,
> Andy
>
> On 14/08/2012, at 11:47 AM, Ian Crossfield wrote:
>
>  It's not quite what you're looking for, but I have Python code to
> generate a wavelength array from the "ec" echelle database IRAF generates:
> http://www.astro.ucla.edu/~ianc/python/nsdata.html#nsdata.dispeval
>
> Kelle's suggestion is probably the easiest, though likely not the fastest.
>
> -Ian
>
>
> On 8/14/12 5:10 PM, Kevin Gullikson wrote:
>
> Hi,
>
> I have some spectra that were reduced in iraf, and I would like to read
> them in to python to do some fitting that I already have code for. However,
> I am having trouble reading in the wavelength calibration. The spectra are
> echelle, and the wavelengths are defined with this thing in the header that
> looks like this:
>
> "
> WAT2_001= 'wtype=multispec spec1 = "1 32 2 10672.221264362
> 0.086046403007761 20'
> WAT2_002= '46 0. 6.65 26.40 1. 0. 1 5 1. 2046. 10761.5346117191
> 87.998952480064'
> WAT2_003= ' -1.32409633589482 -0.0165054046288388 -0.00680394594704411"
> spec2 ='
> WAT2_004= ' "2 33 2 10348.8582697 0.083445037904806 2046 0. 34.60 58.07 1.
> 0. 1'
> WAT2_005= ' 5 1. 2046. 10435.4699172677 85.3379030819273 -1.2833101652519
> -0.01'
> WAT2_006= '53518242619121 -0.0057861452751027" spec3 = "3 34 2
> 10043.881872825 '
> ...
> "
>
> The numbers give the conversion from pixel coordinates to wavelength
> coordinates.
> I was wondering if there was a python function that could correctly read
> all that in, parse it, and give me a spectrum in flux vs wavelength? I have
> tried playing with pywcs but that seems only to work for images?
>
> Cheers,
>
> Kevin Gullikson
>
>
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>
>
>
> --
> Ian Crossfield
> Max-Planck-Institüt für Astronomie
>
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