It is assumed that the Spectrograph is optically complete and that the instrument is mounted via the filter spacer onto the A and G Unit. The orientation of the Spectrograph relative to the A & G Unit must be such that the slit reflection is towards the TV camera. Check that the TV camera, the dekker knob, Hartmann mask control and thermometer are all on the same side of the telescope axis.
NEEDS TO BE UPDATED There are several electrical connections which must be made. The A & G Unit must be connected to its control unit and in turn the comparison arc connected to the power unit on the side of the A & G Unit. The exposure meter photomultiplier has two coaxial leads for EHT (HNC connector) and anode signal (BNC connector). These leads are routed to the Console Area for connection to the exposure meter control box. The shutter, controlled at present from the dome floor, has an electronic box mounted on the instrument casing and hand control paddle on a flying lead. A d.c. supply of 20 to 3O,V is required to power the shutter mechanism. At the time of writing all cabling to the telescope instrumentation was in a temporary configuration.
NEEDS TO BE UPDATED Operation of the A&G Unit is simple. Buttons are pressed to bring either the slit viewing mirror or the comparison arc/direct view mirrors into position. Panel lights indicate the current status and interlocks prevent mechanical fouling of the mirrors and operation of the comparison arc when in the slit viewing mode. A separate push button controls the comparison arc.
OBSOLETE, uncorrected The exposure meter has very few controls. With the mains power 'on' -check the EHT voltage on the panel meter (normally 11OOV). Adjustment is achieved by turning the multi-turn potentiometer with a screwdriver through the hole in the front panel. The digital display can be zeroed or reset at any time by pressing the button under tile display.
OBSOLETE, uncorrected A useful daytime cheek that the exposure meter is functioning can be performed as follows. Illuminate the slit with the comparison arc by operation of the A&G Unit controls. Switch the exposure meter on and open the darkslide in front of the photomultiplier. With the dekker in. either the star or arc position and the slit shutter open, the digital display should count rapidly. With the darkslide or shutter closed, the count should stop (an insignificant count rate corresponding to the dark current will be registered).
Separate instructions are available for operating the TV system and the associated image integration system. It is necessary before observations are started to check that the slit is correctly focused by the TV camera optics. With the A&G Unit in the slit viewing mode and the dome lights extinguished view the slit image on the console display. An assistant will be required to provide some field illumination of the slit area eg., the telescope secondary can be illuminated by a flashlight cautiously. A 1 arc second slit occupies about 2 raster lines of the display. The dull dekker mask should be seen readily against the bright background of the slit jaws. Adjustment of the TV focus must be performed at the telescope by moving the camera body relative to the A&G Unit. A screw system is provided. Careful adjustment at this stage will reduce frustration during observations.