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CosmicLettuce
 10/27/2014 12:49PM (Read 875 times)  
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Newbie

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Registered: 02/08/2014
Posts: 11
I have a FITS file with the following header segment:

% less section.fits
SIMPLE = T / file does conform to FITS standard
BITPIX = 16 / Number of bits per data pixel
NAXIS = 3 / Number of data axes
NAXIS1 = 187 /
NAXIS2 = 774 /
NAXIS3 = 1630 /
.....

However, IRAF is telling me its:

imutil\$this->_split2($m[0]) imhe section.fits
section.fits[187,774,1630][real]:

So while the data is clearly short integers, IRAF is thinking that the data values are real.

In this particular instance, I've got my own software to deal with the data. I'm just using IRAF for data visualization (IRAF is displaying and plotting these images correctly, BTW). But I'd like to know why (or how) IRAF is deciding that this data is 'real' and not 'short'.

Thanks, CL

 
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fitz
 10/27/2014 03:34PM  
AAAAA
Admin

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Registered: 09/30/2005
Posts: 4040
Hacing BSCALE/BZERO header keywords will change the effective pixel type to real even if the values are 1.0/0.0 respectively. These scaling values are often used to produce an unsigned integer range for the data.

 
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