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Acquiring faint objects

If the objects are two faint to see on the slit viewing TV then they should be acquired using the TCS BLIND_OFFSET command. For each object the observer should bring accurate positions of the object, and of an offset star which will be visible on the slit viewing TV. Each position should be entered as a catalogue entry in the TCS. The procedure for acquisition is as follows:-

1. Acquire the offset star on the rotator centre by typing GOCAT <offsetstar>.
2. Centre the star up on the rotator centre using the handset.
3. Move the star into the slit with the APERTURE command.
4. Move to the programme object by typing BLIND_OFFSET <objectname>.

Once the object is centred on the slit it is possible to begin the CCD integrations. The WHT tracks well enough that it is standard procedure to begin the integrations before acquiring a guide star. Integrations are started with RUN, and can be the same length or different lengths. If they are the same length, and the frames are large, then the two CCDs may be reading out into the DMS buffers simultaneously; the DMS is capable of handling this, although the message ``Reading CCD'' on the DMS screen may disappear after the first CCD has finished reading out, although the second has not yet finished. The DMS command ?REGS allows one to check whether the CCDs have all finished reading out.