Ian Crossfield ianc at mpia-hd.mpg.de
Thu Jul 4 05:06:57 EDT 2013

```The previously suggested solutions work for a linear wavelength
solution, but things get more complicated for higher-order polynomial
relations.  In these cases I use the following:

from pyraf import iraf
import numpy as np

I agree that it would be convenient to have an AstroPy helper function
for doing this sort of thing.

-Ian

On 7/4/13 10:57 AM, Thøger Rivera-Thorsen wrote:
> I usually go:
>
>
> That should be about as simple as it gets :-)
>
> Cheers,
> Emil
>
>
>
> On 2013-07-04 10:43, Éric Depagne wrote:
>> Le jeudi 4 juillet 2013 à 03:51:20, Gustavo Bragança a écrit :
>>> Hi,
>>>
>> Hi Gustavo,
>>
>>> Is there any easy way to load the values of wavelength from a FITS spectrum
>>> using astropy?
>>>
>>> I could obtain the wavelengths by using some values of the header, but I
>>> was wondering if there is an easy way.
>>>
>> I use the following code to get the wavelength and intensity:
>>           f = pyfits.open(fitsfile)
>>           start = crval1 - f[0].header['CRPIX1'] * cdelt1
>>           end = start + cdelt1 * f[0].shape[0] - cdelt1/10.
>>           x = numpy.arange(start, end, cdelt1)
>>           f.close()
>>           return x, f[0].data
>>
>> I'm not sure it's the best way to do so, but it works.
>>
>> HTH.
>>
>> Éric.
>>
>> Un clavier azerty en vaut deux
>> ----------------------------------------------------------
>> Éric Depagne                            eric at depagne.org
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--
Ian Crossfield
http://www.mpia-hd.mpg.de/homes/ianc/
Max-Planck-Institut für Astronomie
+49-(0)6221 528-405
Room 308/4

```