Best focus position of the pupil lens

We have the laser fiber in the bumper and the stopped-down pupil mask with a bearing placed in the 1/4" hole to provide a target on which to test the focus.

The target image appeared to be very sharp on the grating and at the collimator (seen below on a card just forward of the collimator mirror).

As a starting point for the 1" KRS5 pupil lens, Joe and I placed 14 mm into its lens wheel barrel, (see post "Current Lens Wheel Configuration")

For this test, I took images with the bare-MUX and red laser with the KRS5 lens placed at different positions in the barrel.

From left to right, these distances are: 13.1 mm, 14.3 mm (closest to calculated value), 15.2 mm, 16.2 mm, 17.3 mm, 18.3 mm.
Visually, 17.3 mm seems to be the best focus. Using the 1" KRS5 lens in this position we will try to align the ellipsoid while EXES is on the TAS.