The dichroics are tilted using three collimating screws on the dichroic holder. The relevant dwg for the dichroic is the assembly dwg 111809, and the adjustment screws are labeled 2H. In the assembly instructions, item 15 states "During collimation with the cell in the spectrograph, it has been noted that the friction of the spring plungers on the ground glass edges of the dichroics is higher than was noted with tests using a machined aluminum dummy dichroic. To ensure contact on the collimating screws if a screw is backed out, slight pressure should be applied to the front surface of the spring plate. As tilt adjustments are made, try to balance them with the top and bottom and left and right screws to maintain the nominal position adjustment."

When looking at the adjustment screws, there are three adjustments: two on the top and one on the bottom.

When looking at an image of the grid of holes
• Clockwise on top and counter clockwise on bottom will move the grid of holes to more positive X values. 1 turn is 280 pixels.
• Clockwise on Top left and counterclockwise on top right will move grid of hols to more positive Y. 1 turn = 367 pixels.

Goal of alignment: Acquire images with the grid of holes mask. We have identified six pixels in the grid to help maintain alignment. The most critical direction to maintain is is the detector X alignment so that objects do not fall in the blue side gap.

The following positions are reference pixel locations.
1. 694.02, 982.06 - first row of holes
2. 2091.44, 983.30 - near gap
3. 3454.73, 983.04 - last row of holes
4. 678.77, 3151.03 - first row of holes
5. 2089.04, 3145.31 - near gap
6. 3462.36, 3152.42 - last row of holes

In the tables below, we are tracking the adjustments made for each dichroic. The screw positions are labeled as seen from the back with the palm handle up. All motion is relative to the commissioned positions. Negative values are counter clockwise turns while positive values are clockwise when looking at the screw head with the palm handle up.

680

560

500

460