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Below-the-Slit Viewing

Viewing the aperture plate from below the slit is accomplished by positioning a flat mirror on a rotating arm into the beam below the slit. This arm is stowed safely out of the beam in a detent, and the detent itself is moved for the arm to seat in viewing mode. The detent is moved by a black knurled wheel [I] on Side 1 of the spectrograph, in the black cylindrical housing. The word thru should be visible on the black knob. Turn it clockwise past chop until it settles at view. Then turn the double-handled brass crank a half-turn counterclockwise until the arm is seated in the new detent position. Make sure the Schmidt camera shutter is closed (see Chapter 10) and open the slit shutter to view with the eyepiece [H] the field transmitted through the aperture. This beam is affected by both the upper and lower filter wheels (see Chapter 7), and the procedure must be reversed to assure that the spectrograph is illuminated by an unvignetted beam.

Pat Hall - Wed Oct 4 11:02:37 MST 1995