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For multi-object spectroscopy, the acquisition of the field is performed by means of an aperture plate of type FOCAP. This aperture plate is a 3mm thick brass plate. The plate is drilled at precise locations with holes to accept fibre connectors. The holes must be made for each of the three types of connectors: for the individual fibres, for the two semi-coherent bundles and for the coherent bundle. The characteristics of the holes are specified in the Table 5 (it is assumed that the OY+ direction corresponds to the North direction during the observing epoch).
The vertical displacement that the coherent bundle has with respect to the object coordinates allows it to be observed by the northern part of the bundle, where the packing quality is best (see section 2.12.3).
A high precision (on the order of 20 microns) both for the coordinates and the hole diameters is fundamental for accurate field acquisition.
The number of holes to be performed for each type of connector is as follows:
The aperture plates can be made by the CAMM3 engraving machine, in the same way as the multi-slit masks. Observers wishing to use the fibre system should provide accurate co-ordinates for aperture plate manufacture to La Palma staff at least one month in advance of the observing run.