To change filters in the auxiliary filter unit the CCD cryostat and the auxiliary focus filter unit must be removed from the telescope. The former operation must be carried out by technical staff, and it is very unlikely that this will be possible during the night. With the cryostat removed, the cables connecting the shutter to the CCD controller and the filter wheel to the A&G box 4ms must be removed from the front plate of the auxiliary filter unit. The filter unit then can be removed by unscrewing a number (up to 12) small allen screws around the front plate, and lifting the front plate, to which the filter wheel is attached, off. The filter wheel is a standard INT wheel, and the filters are changed in a similar manner, they are held in place by spring loaded cylindrical washers. The washers can be mounted either way up on their posts, to allow for filters of different thicknesses.