Lumicon 2" diameter × 2" length — Thread-In Eyepiece Extension Tube Color Filter The standard Bahtinov mask is

The standard Bahtinov mask is the simpler option if you only need focus assistance — same drop-in fit

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Compatible with GSO/William Optics Early Version Crayford Focuser w/o Microfocuser

This handle is part of the FDA family — every member shares the same quick-release base

Lumicon 2" diameter × 2" length — Thread-In Eyepiece Extension Tube Color Filter The standard Bahtinov mask isLumicon 2" Thread In Extension Adds 2" of back focus so your eyepiece or camera can reach sharp focus. The Lumicon 2" diameter 2" length Thread In Eyepiece Extension Tube threads into a 2" eyepiece to add up to 2" of focus extension. A compact spacer for fine tuning where your eyepiece sits in the focal path. The larger 2" clear aperture suits wide field eyepieces and large sensor imaging, where it reduces vignetting compared with a 1. 25" light path.