1. Dirt or dust on thge slit causes 'bad rows' on detector
 Date: 14/01/1998 (all pixel positons refer to TEK3+500mm camera).
 
 Always check the IDS slit-profile with a flat field before setting
up your window and position of star on the slit. There appears to 
be some dirt or dust on the slit between pixels y=455-620.
This results in what looks like bad rows on the CCD. 
With carful placement you can put your star in between these 
'bad rows'. But a better solution is to use rows y=620 - 820 
which are relatively free. Note that that between 820 - 910 ther is
some vigentting, and beyond y=910 the vigentting is very severe.  
 The slit will be cleaned the next time IDS comes off the telescope, 
as it is impossible to get to otherwise.