[AstroPy] question on saving fits files

[Doug Burke]

Grigoris,

If you change 'dt = dt * 1000' to 'dt *= 1000' do you get what you expect?

Doug

On Wed, Feb 10, 2016 at 11:30 AM Grigoris Maravelias <
gr.maravelias at gmail.com> wrote:

> Hello!
>
> I have a problem with a rather simple process, but I cannot understand
> what I am doing wrong. I have an image in a fits file that i want to
> open and process its data values, and save it as another file (including
> some extra information on the header for what I did). So according to
> the astropy docs [1] I did the following:
>
> hdulist = fits.open('small.fits')
> hdu = hdulist[0]
> hd = hdu.header
> dt = hdu.data
>
> hd.append(('HISTORY', 'blabla '), bottom=True)
>
> print dt            # check data before
> dt = dt*1000
> print dt            # and after
>
> hdulist.writeto('small_mod.fits')
>
> If I print dt before and after their modification (multiplied by 1000) I
> can see that they are indeed different (properly multiplied), but when I
> save the fits file I just see the original data values (however, the
> HISTORY line is added properly in the primary header).
>
> What am I missing here?
>
> Best
> Grigoris
>
>
> [1] http://docs.astropy.org/en/stable/io/fits/usage/headers.html
>
>
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