The spider assembly consists of stainless steel vanes, lugs and central rings. All fasteners are stainless steel. The central hub, plates, cell and ribbing are carbon fiber/high temp epoxy. The use of low CTE carbon fiber parts in these locations prevents optical movement and pinching of the optics, which can occur when aluminum is used.

The upper rings and carbon fiber central hub allow for gross placement of the secondary mirror in: tip/tilt, rotation, axial and lateral positioning.

Once the secondary mirror is roughly in place, rotation can be fine tuned using the rotation assembly. This assembly sits just below the main spider hub and just above the main secondary support ribbing. This rotation contol is independent of all other adjustments and greatly improves collimation control and ease of use.

This is a second generation assembly that offers fine tip/tilt down below the central hub, as well as rotation adjustment, already mentioned. The new design also greatly improves the air flow to the back of the secondary mirror. The height of the central vanes was increased (increased stiffness) and the vanes were opened up.