Viewing the aperture plate from above yields about a 2.5.5
arcmin field (
mm). Normally, the acquisition TV camera
[B] views the aperture plate from above. To see the
same picture visually, a relay mirror directly above the TV must be
rotated by turning the selector knob [P] so that the handle indicator
aligns to horizontal. Uncap the viewing eyepiece by pulling off the
captive cover [J] and focus by twisting the threaded eyepiece holder.