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Observing with IPCS only or with CCD and IPCS

Procedures for setting up and using the IPCS are described in full in The IPCS-II Users' Manual, by J.S.B. Dick and it is important that observers who intend to use the IPCS read this manual.

The IPCS is easily damaged by bright light. Thus it is important that before opening the shutter the observer should be aware of the degree of illumination which will fall on the detector. If the observer is unsure of this, then they must insert neutral density into the beam with MAINFILTND (or alternatively with COMPFILTA or COMPFILTB if the exposure is of a comparison lamp, and gradually reduce the level of neutral density until the level of illumination is the maximum that can be tolerated. Unlike the CCD systems, starting and ending IPCS exposures is independent of the operation of the shutter. The shutter can be opened with the command IPO, and closed either with the command IPC, or by pressing the ``Panic Button'', but this does not mean that an exposure has been taken. An exposure should be started with the command EXPOSE IPCS after the shutter has been opened; and the shutter should be closed with the command IPC immediately an exposure has ended.

The ``Panic Button'' is present to enable the user to close the shutter immediately if the level of illumination is too high. If this is used, the software does not know that the shutter has been closed, and the observer must also close the shutter in software with IPC before the software will allow the shutter to be opened again.

If the shutter is opened and the level of illumination is much too high an overillumination trip will occur. This causes the shutter to close, and an overillumination status to be set in the IPCS 4ms; the shutter cannot be opened until this status has been cleared. This can be done with:-

OVERILLUM_INIT

It is important to establish the cause of the overillumination trip before opening the shutter again. An overillumination trip does not affect the EHT supply, and thus does not provide any protection in case of shutter failure, and provides only limited protection if the cause of the overillumination is lights in the dome.

• TV Focus
• Switching on the IPCS EHT voltage
• Instrument Calibration Data
• Acquiring data on the sky