Be aware that currently (SV1 stage) there is no correction either for cross talk images are persistence images in the pipeline. A bright star may cause a persistence image in subsequent images (rapidly decaying). Cross talk manifests itself as a spurious image in a channel adjacent to a channel containing a bright star. The cross-talk image appears as the spatial differential of the original image. Therefore typically it is an odd-even image, as in the example below.

• crosstalk2.jpg:
  

If the bright star is saturated however, its image is flat-topped in the centre, so the differential is zero in that part. This gives rise to ring or washer-shaped images. An example is given below. The chances are you can identify them as they should have class=-2 (a star has class=-1).

• crosstalk1.jpg:
  

-- SteveWarren - 03 Aug 2005