Subject: Re: ST6 to Fits

From: [email-masked] (Doug Snyder)
Date: Fri, 10 Jun 1994 23:59:28 GMT

Malcolm Currie ([email-masked]) wrote:
: In article <[email-masked]>, [email-masked] (Dominique Beauchamp) writes:
: |>
: |>The ST6 operating software allows you to save the images in FITS.  I think however
: |>that they are saved as UNSIGNED 16 bit integers, which is not supported by FITS.
: |>Then youu should add in the header BZERO=16384... (I think...).

: Shouldn't that be BZERO=32768?

The ST6 software does allow saving files as FITs; you have the option of
saving as 8 bit or 16 bit. I attempted both of these on a standard .st6
file and then loaded the resulting .img files into the PC pgm IMDISP
(available free from the JPL ftp site).  In viewing the header info
for each .img file, there is no header line BZERO in the 8 bit image,
but there is a BZERO=32768 line in the header for the 16 bit image.
However, in the IMDISP program, I was able to view and do image
manipulation on the 8 bit .img image, but nothing appeared on the screen
after loading the 16 bit .img file. The program said it had loaded the
image (the 16 bit one), but I was unable to obtain any screen display
and no error messages were present, so I'm not certain if I neglected
to do something else to bring up the 16 bit display or if there is
some other data in the header that is different or missing. Hmmmm.
In comparing other 8 bit images that came with IMDISP, they also do
not have a BZERO line in the header. There was no 16 bit image to do
a comparison with. BTW, the extension .img is used in the IMDISP with
their image files, so that is what I used when converting the .st6
files to FITS.