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Target acquisition tools

Precise target acquisition is particularly crucial process for a multi-slit spectrographs. This is because of the need to align the mask, within three degrees of freedom, so that each object is positioned at the centre of its intended slit.

There will be several standard procedures to aid in this process. Here will simply outline the specialised commands which may be used:

• CREATE/MASK: if there is a MASK list in the stack it is used to generate a new FIBOX list which consists of boxes defined so as to surround each slit in the mask. This is useful for finding the centroids of slits in a direct image of the mask. This may be used in conjunction with FIT/LINE.
• FIDUCIAL: takes the output FIBOX list from CREATE/FIDUCIAL and locates the centres of the fiducial holes.
• FIT/FIDUCIAL: then locates the stellar centroids within the windows found by FIDUCIAL.