HP 8568B Performance Tests And Adjustments Manual page 178

4. Final Display Adjustments (SN 3004A and Above)
3-64 Adjustments
17. Adjust AlA2R512 ORTHO and the front-panel ALIGN control
to optimize the orientation and appearance of the rectangular
graticule pattern on the CRT display.
18. Repeat steps 13 through 17 as needed to optimize overall display
focus and appearance.