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Alignment of the CCD is such that
the long axis of the detector corresponds to the long axis of the TV although
the TV scan causes the RA axis to be slightly tilted to the long axis of
the chip. This position corresponds to E-W on the sky and to a Cassegrain
rotator position of 359.2 degrees. The TV should be parfocal with the CCD and
the autoguider although when the telescope is refocussed the TV will be slightly
out of focus.
Figure 3 shows the views which are obtained if the Lexidata display is set
up so that the CCD frame origin (x=0, y=0) is located at the lower left-hand
corner. The long axis of the chip is arranged so that it corresponds to
the long axis of the TV. The TV scan switches must be H (up) and V (down).
The Cassegrain rotator should read 0.
When the grisms are being used the directly-viewed object should be centred 60 arc seconds west of the chip centre. The dispersion direction is also along the long axis of the chip.