Acquisition and guidance

Most of the ING telescope foci are equipped with a dedicated acquisition and guiding unit. In most cases the use of these A&G facilities in conjunction with user supplied instruments is fairly straightforward. In some cases the instruments themselves will have some A&G capability, however it will often be difficult to interface these with the existing telescope operation. For example, it may be necessary to use long ladders to access eyepieces. In some cases it may be possible to modify these facilities, to allow for example a standard ING TV camera to be fitted to an eyepiece holder. The following list summarises the A&G facilities available at each of the ING telescope foci.

• WHT f/11 Cassegrain focus: The WHT Cassegrain A&G unit will provide a comprehensive range of acquisition, guiding and calibration facilities. See Section for a detailed description. The slit-viewing axis bisects the 16 mounting hole pattern (i.e. displaced 11.25 from a hole centreline)

• WHT GHRIL laboratory: Guiding is possible using a Westinghouse TV camera or CCD Autoguider and pellicle (95%/5%) beamsplitter mounted on an aluminium jig. With the derotator it is possible to guide on an off-axis guide star; without the derotator it is necessary to guide on the target. Please contact the GHRIL manager for further details.

• INT f/15 Cassegrain focus: The INT Cassegrain A&G unit provides a wide range of useful facilities. See Section for a detailed description. There is scope for modification and adjustment to cope with some non--standard configurations with user supplied instruments. The slit viewing optics works at the standard 15 angle (7.5 slit tilt) at the nominal 150 mm back focus. The optical axis of the slit viewing system is oriented to bisect the 12 M10 instrument mounting hole pattern.

• INT f/3.3 prime focus: The INT prime focus is equipped with its own autoguider which can access half of the avaliable 40 arcmin field. See Section for a more detailed description. The usual method of acquisition at prime is to use the finder telescope, however it is possible to run one of the spare integrating TVs if this is required for a user instrument. The CCD mounting for prime is equipped with a filter wheel and fast shutter which could also be used with a user instrument.

• JKT f/15 Cassegrain focus : Two possible A&G units are available, described in some detail in Sections and .

  The original general purpose unit provides a TV, direct acquisition and slit viewing optics, and a calibration lamp. This general purpose A&G unit is designed to be used with the standard instrument mounting with 150 mm back focus. The slit viewing optics works at the standard 15 angle (7.5 slit tilt) at the nominal 150 mm back focus. The optical axis of the slit viewing is orientated to bisect the 12 M10 instrument mounting hole pattern (i.e. displaced 15 from a hole centreline) .

  A newer A&G unit is also available, dedicated for use with the CCD camera. This has a three point kinematic mounting to match the standard CCD cryostats. The A&G unit has a standard acquisition TV, offset autoguider, filter wheel and fast shutter, as well as a pair of low dispersion grisms. The disadvantages of this A&G unit are a reduced back focus clearance of only about 16 mm ,a reduced field of view of 270 arcsec (20 mm) and no slit viewing facilities or calibration lamps.