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TAURUS can be used with two different cameras. This section describes the process for changing the camera. Note that this is a daytime job, since it involves removing the detector.
Both the f/2.1 and f/4 cameras are mounted on kinematic seats and tilt adjuster screws which allow them to be initially aligned and then repositioned accurately. The original intention was to have a seperate set of screws for each camera, however these proved difficult to install and it was found that the two cameras were sufficently aligned if they used the same screw settings. This alignment was checked using the f/2.1 camera alignment as a reference since it had previously been accurately set with respect to the collimator and instrument body axes. A HeNe laser was mounted on a tilting stand on the on the Al alignment T--piece. The laser was first roughly aligned in translation with the centre of the lens cover. The reflected spots from the optical components of the f/2.1 camera were observed on a small white screen in front of the laser. By subsequent iterations of translation and tilt all the reflected spots could be made coincident and the laser was now aligned with the optical axis. The f/4 camera was swapped for the f/2.1, the reflected spots were now within 3mm in the 800mm distance to the laser. This is equivalent to a maximum tilt of 0.1 degrees which has no significant effect on the optical quality, especially if the CCD tilt is adjusted. It is thus possible to swap between f/2.1 and f/4 cameras without the need for adjustment.
To install the camera, the lower section camera box is lowered from the back of TAURUS and the cameras inserted from the top after first removing the 3 screws from the underside of the box which clamp the camera to its kinematic seat (be careful not to move the smaller tilt adjuster screws by mistake). The easiest way to lower the camera box is to use the rising floor and trolley whilst TAURUS is on the telescope.