The M81 → M54 (female) adapter with stop ring for ESATTO 3" / ARCO 3" (PrimaLuceLab, SKU: PL3600275 ) enables the connection of accessories with an M54 × 0.75 male thread (e.g. filter wheel, adapters, cameras) to the ESATTO 3" focuser or ARCO 3" rotator, which have an M81 × 1 front thread. The integrated stop ring allows you to precisely set the adapter's screw-in depth and lock it in the selected position, which facilitates back-focus control and orientation of the connected device.

Key Features

• thread conversion: input M81 × 1 (ESATTO 3" / ARCO 3") → output M54 × 0.75 (female)
• stop ring – precise position adjustment and secure adapter lock
• optical thickness of only 7 mm – minimal impact on the back-focus budget
• full internal diameter 54 mm – no vignetting for APS-C sensors
• 6061-T6 aluminum body, hard black anodized – lightweight, stiff and corrosion resistant
• blackened, grooved interior – effective reduction of reflections and ghosts

Set components

• M81 → M54 adapter with stop ring
• Allen screw locking the ring

Technical parameters

• input thread: M81 × 1 (female)
• output thread: M54 × 0.75 (female)
• optical length: 7 mm
• Inner diameter: 54 mm
• material: aluminum 6061-T6, black anodized
• compatibility: ESATTO 3" lift, ARCO 3" rotator, accessories with M54 × 0.75 thread
• EAN: 8059020773250
• manufacturer: PrimaLuceLab – Italy

PL3600275 is a practical accessory that allows you to connect the wide ESATTO 3" focuser or ARCO 3" rotator with popular accessories in the M54 standard, maintaining full control over the back-focus and mechanical stability of the entire optical system.