Changing the Grating

To change gratings, one must take care to protect the detector package if it is powered up. The Schmidt camera shutter (see below) should be closed and dome lighting minimized. Gratings are stored in two wooden boxes in the filter storage room. Refer to the illustrations in Appendix A for the bracketed letter identifications.

Use the following procedure to change gratings:

1. Protect the Schmidt camera by switching its shutter lever [W] closed (see Chapter 10).
2. On Side 3 of the spectrograph is a black port cover [Q] with a handle and three knurled knobs. Loosen the knobs and rotate the cover CCW and lift it off gently.
3. If there is a grating in place, close its cover by pushing the red cover slide in until it hits a hard stop.
4. Unlock the grating by turning the half moon handle CCW 90 degrees, i.e. until its flat surface is parallel with the grating holder. Gently pull the grating holder out, pulling on its black handle. If there was no grating, just make sure the half-moon handle is fully CCW.
5. Insert the new grating with its red cover slide closed.
6. Lock the grating in place by turning the half-moon handle fully CW (flat surface perpendicular to the grating holder), then open the grating cover by pulling out the red cover handle, extending the cover slide fully until it hits a hard stop.
7. Put the black port cover back over the port hole, twist it CW, and tighten the knobs.
8. Reopen the Schmidt camera shutter.