Bob's Knobs for FPI Protostar Secondary: Precise and Convenient Collimation Specially Designed for FPI Protostar: Tailored for FPI Protostar secondary assemblies that use a 8-32 x 1 inch long set screw for collimation adjustments. Part Details - Part: FPIsec8: Telescope Compatibility: Perfectly fits FPI Protostar secondary assemblies with specified collimation screw dimensions. Knob Features: Constructed from black plastic, each knob is 13 mm (1/2”) in diameter, ensuring easy grip and precise adjustments. Thread Quality: Features durable stainless steel threads for a secure and lasting connection. Usage Considerations: Specific Fit: These knobs are compatible with FPI Protostar secondary assemblies that use 8-32 x 1 inch long set-style collimation screws. Light Path Note: The outside edge of each knob may slightly extend into the light path. Enhanced Telescope Tuning: Ideal for astronomers with FPI Protostar secondary assemblies seeking a simple, tool-free solution for accurate and easy collimation adjustments.