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Reconfiguring the control software for Prime Focus

The control software is initialised from two text files, one containing quantities which do not depend on the focal station or instrument (e.g. the servo constants and Camac addresses), the other containing focus-specific data such as pointing coefficients. The two files for the INT prime focus are called INT.STD and INTPFCCD.STD respectively. Immediately after the prime focus top end is installed, the telescope control software must be loaded by typing:

GO INT,INTPFCCD,COMPILE

on the system console of the telescope control computer.

Subsequent GO commands can be of the form:

GO INT

This is because the COMPILE option generates two binary files called INPSCF.SYM and INPSCF.VAL which can be read in much more quickly than the .STD files but contain the same information. However, they cannot be edited and have to be regenerated every time the .STD files are changed (i.e. after an end change or if the .STD files are edited). When the Cassegrain secondary is replaced, the control software must again be reconfigured by typing:

GO INT,INTCASS,COMPILE

If in doubt, always use the COMPILE option for the appropriate top end. This can never do worse than waste a few minutes. The GO command objects if you type an illegal command format or if any of the input files do not exist, so it is impossible to initialise the control software with the pointing coefficients missing, as has happened in the past. If you are suspicious that the software thinks that the wrong top end is on, look at the Information Display. If the Cassegrain rotator angle is displayed (compare with the Engineering rack, remembering that the numbers are complementary - one is minus the other), then you have the Cassegrain software and need to recompile. It is worth moving the rotator by a small angle to make sure that the display changes to avoid the coincidence of the prime and Cassegrain PAs being the same. The prime focus rotator PA will not be displayed until it is sent over the interprocessor link by the instrumentation computer, so the display may initially be blank. Alternatively, look at the aperture offsets when the telescope is in the ``beamswitch nominal'' position. The total offset (i.e. the square root of the sum of the squares) should be 600 arcsec. For the Cassegrain system, it will be much smaller. A definitive test to check on initialisation uses INPSCF. Look at the values of the variables LOCATE and IFNUMB. These are the telescope identifier (1 for the JKT, 2 for the INT) and the focal ratio (3 for prime, 15 for Cassegrain on the INT), respectively. LOCATE is loaded from the telescope file, IFNUMB from the focus file.