Description The OPTEC-4300 12.5mm Extension Ring provides approximately 1/2-inch of extension for any OPTEC-4300 telescope adapter. Ideal for telescopes where the Gemini Focusing Rotator may need to pushed out and away from the OTA to provide clearance for cooling fans or when a little extension is required to reach optimal focus. Specifications Inside Diameter: 3.9" (99mm) Outside Diameter: 4.95" (126mm) Overall Height: 0.81" (20.6mm) Clear Aperture: 3.9" (99mm) Weight: 5.0 oz (145 g) Back-Focus Usage: 0.492" (12.5mm) The OPTEC-4300 12.5mm Extension Ring provides approximately 1/2-inch of extension for any OPTEC-4300 telescope adapter. Compatibility Any OPTEC-4300 telescope adapter. Gemini Focusing Rotator. TCF-Lynx3 3-inch Focuser. The OPTEC-4300 12.5mm Extension Ring provides approximately 1/2-inch of extension for any OPTEC-4300 telescope adapter.
