FITs to TIFF, why the added offset/pedestal?

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stevel

FITs to TIFF, why the added offset/pedestal?

Post by stevel »

Hi all

Version: ImageMagick 6.5.7-0 2009-10-15 Q16 OpenMP http://www.imagemagick.org

I am converting FITs files to TIFF, but am wondering why there appears to be an offset/pedestal added (approx 21,000 by the looks of it). Here is the histogram of the original FITs file.

Image

and here is the histogram of the converted TIFF file

Image

I am just using the default convert without any options, and the verbose output looks like this:

Code: Select all

m13_idas_190mn_x2_-024.fit FITS 3032x2016 3032x2016+0+0 16-bit DirectClass 11.66MiB 2.375u 0:02.375
m13_idas_190mn_x2_-024.fit=>m13-tiff-out.tif FITS 3032x2016 3032x2016+0+0 16-bit Grayscale DirectClass 11.67MiB 0.094u 0:00.110
Does anyone have any ideas as to what is happenning, or what options I need to enable to prevent the data having this offset added to it??
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