unsigned images

[Steve Allen]

In article <owen-ya023080001902971414190001 at news.u.washington.edu>,
Russell E. Owen <owen at astro.washington.edu> wrote:
>I have great antipathy to converting all my data as its written, and then
>converting it again as it's read out. Like most night-time astronomical
>applications, our cameras all produce 16-bit unsigned data. It is a huge
>advantage to be able to read and write this data in a single operation
>w/out converting it first.

Only two steps are necessary.

1) flip the high order bit of each pixel
	(if your CCD controller has DSP capability this can be done as
	part of the data pipeline so that you incur no delay)
2) set BZERO in the FITS header.

Then you have standard BITPIX=16 FITS images.
No modification to existing standard is required.
--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
sla at ucolick.org      Voice: +1 408 459 3046     FAX: +1 408 454 9863
WWW: http://www.ucolick.org/~sla                PGP public keys:  see WWW