After moving the collimator mirror, run goSpecFocus again to make sure the red camera is in focus. Once you are happy with the red camera's focus, then run the program this time to take the blue Hartmann images (using the HgCd lamps) and calculate the pixel shifts. The calibration is that a delta-shift=+1 pix in the blue Hartmann images requires movement of the blue-camera focusing ring by -35.7 degrees. goSpecFocus outputs the required number of degrees to turn the focusing ring and exits - this correction must be done physically at the back of the telescope.

First unscrew the thin lock ring (located above the focusing ring) which will allow you to move the focusing ring. When moving the focusing ring, the last move should turn the ring more then 90 degrees clockwise (i.e., 1/4 turn INTO the spectrograph). If the instructions from goSpecFocus require moving the ring away from the spectrograph (i.e., counter-clockwise), overshoot your final destination more then 90 degrees so your final movement is 90 degrees into the spectrograph (1/4 turn cw). If the instructions require moving the ring in towards the spectrograph by less than 90 degrees, first move the ring enough in the opposite direction so that your final movement is greater then 90 degrees into the spectrograph (1/4 turn cw). Block the focusing ring with the thin lock ring after you are done.

When the locking ring correction has been applied repeat goSpecFocus to check the focus is correct (if not apply the new corrections and repeat again). After a good focus has been established, take another flat and arc and make sure the flat and arc characteristics reported by Son-of-Spectro are still within their tolerances.