[AstroPy] Pyfits nan issue

Perry Greenfield perry@stsci....
Mon Sep 14 10:06:39 CDT 2009


After looking at the file, it may be an issue with how pyfits is  
dealing with compressed data. We won't be able to look at it right  
away, but we will fix it at some point in the next month or so.

Perry

On Sep 11, 2009, at 2:48 PM, Tommy Grav wrote:

> I am trying to read in images using the pyfits svn trunk
> (2.1.1dev494). These images
> display correctly in ds9, but when reading in pyfits the nan values
> are converted to
> very large values (well not that large, for example 53662.75, but with
> different values
> for each image).
>
>>>> hdu.info()
> Filename: o5014g0242o.84241.wrp.7117.skycell.077.fits
> No.    Name         Type      Cards   Dimensions   Format
> 0    PRIMARY     PrimaryHDU       6  ()            int16
> 1                CompImageHDU    98  (6000, 6000)  float32
>>>> hdu[1].header["BITPIX"]
> -32
>>>> np.isnan(hdu[1].data).sum()
> 0
>>>> hdu[1].data.max()
> 53662.75
>>>>
>
> Does anyone know what might be going on such that ds9 correctly reads
> the files and
> displays the nan values, while pyfits (or np) fails to do so?
>
> Cheers
> Tommy Grav
> +
> ----------------------------------------------------------------------------+
> Associate Researcher @ Dept. of Physics and Astronomy
> Johns Hopkins University
> +
> ----------------------------------------------------------------------------+
> tgrav@pha.jhu.edu
> (410) 516-7683
> http://web.mac.com/tgrav/Astronomy/Welcome.html
> +
> ----------------------------------------------------------------------------+
>
>
>
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