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		<subject index="0" >Re: CALIBRATION</subject>

		<tonames index="0" >S194 06E real time observing</tonames>

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As Dave says, all these calibration images are the type of things students on SXR208 get a lot of practice with!!

Here's one of the flat-field images.

I've saved the raw format ('FITS files' = Flexible Image Transport System)
as a pdf file - you'll need Acrobat installed to see these - I guess most people have it?

Notice the structure here - bright in the middle and darker round the outside.
This is the 'vignetting' due to the opticsand is an effect that needs to be removed from 
the target observations using images like this.

Notice also the various blemishes due to dust and muck on the mirrors andfilters.
Again all this gets removed from the target images using these flat field images.

Andy