OBSOLETE, uncorrected With a plate loaded mount the plateholder on the Spectrograph noting that there is only one correct orientation for this unit defined by the three kinematic mounting locations and anti-fouling pins. The Plateholder slide should be moved to one end of its travel (with the I scale reading 22mm or 12mm). -exposures are normally conducted with @:t slide in positions 22, 19. 5, 17, 14. 5 and 12 mm. The '22mm' exposure., occurs near the middle of the plate and the 12-.mm exposure at the edge the plate.
NEEDS TO BE UPDATED Ensure the slit shutter is closed, the dekker is in the star position, the Hartmann mask is ``in'' and the plateholder darkslide ``out''. The focus micrometer should read 0.2,mm greater than the anticipated focus (5.0,mm for blue optics, 4.5,mm for red optics). With the slit illuminated by the arc source, the slit shutter should be opened for about 10 seconds thus exposing the plate. Without moving the plateholder a second, exposure should be made with the Hartmann mask in its detented location and the dekker in arc (double aperture) position. The plateholder can then be moved to the next location and the micrometer focus screw decremented by 0.1,mm. The exposure cycle is repeated keeping the mask and dekker in the same relative locations throughout i.e., mask ``in'' , dekker ``in'' and mask ``out'', dekker ``out''. The plate should show a total of five focus tests conducted at settings of e.g., 5.2, 5.1, 5.0 , 4.9 and 4.8,mm. The darkslide must be closed before removing the plateholder!
The resultant spectra should show a shift in the relative positions of the ``arc'' and ``star'' exposures as in the classical Hartmann test. The best focus should be determined and the micrometer set to the nearest 0.05,mm and the Spectrograph temperature noted. A change of more than 5,C will require a new focus to be set or determined depending on the calibration data available. Based on experience with a similar spectrograph in St Andrews the temperature coefficient of focus change will be about 0.025,mm/,C.
The Spectrograph should now be ready for astronomical observations. Any pre-slit filters should be prepared for use.