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WHT Cassegrain Slit-Viewing TV

To help to determine which direction on the CCD corresponds to which direction on the sky, the following information is needed which links the ROTSKYPA angle in the image header to the TV viewing orientation. The ROTSKYPA is, (as you can probably guess!) is the Parallactic angle of the Cassegrain Turntable on the sky. 
                                             East
                                            /|\
                                             |            
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For PA=0, the directions on the TV are:      |
                                              ------------> North


For PA=90, the directions on the TV are:      ------------> East
                                             |
                                             |
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                                            \|/
                                             North
The slit is ALWAYS viewed lying left-right on the TV no matter what the PA of the rotator is i.e. the TV is permanently fixed with respect to the slit.