The M81 → M72 (female) adapter with stop ring for ESATTO 3" / ARCO 3" (PrimaLuceLab, SKU: PL3600272 ) enables the connection of accessories equipped with an M72 × 1 external thread (reducers, flatteners, filter wheels) to the ESATTO 3" focuser or ARCO 3" rotator, whose front thread has a diameter of M81 × 1 . The integrated locking ring (stop-ring) allows you to precisely set the screw-in depth and lock the adapter in the selected position, facilitating the maintenance of the correct back-focus and orientation of the connected device.

Key Features

• thread conversion: input M81 × 1 (ESATTO 3" / ARCO 3") → output M72 × 1 (female)
• stop ring – precise position adjustment and secure adapter lock
• optical thickness of only 7 mm – minimal impact on the back-focus budget
• full 72mm internal diameter – no vignetting for full frame sensors
• 6061-T6 aluminum body, hard black anodized - lightweight, stiff, corrosion resistant
• blackened and grooved interior – effective reduction of reflections, better contrast

Set components

• M81 → M72 adapter with stop ring
• Allen screw locking the ring

Technical parameters

• input thread: M81 × 1 (female)
• output thread: M72 × 1 (female)
• optical length: 7 mm
• Inner diameter: 72 mm
• material: aluminum 6061-T6, black anodized
• compatibility: ESATTO 3" lift, ARCO 3" rotator, accessories with M72 × 1 thread
• EAN: 8059020773281
• manufacturer: PrimaLuceLab – Italy

PL3600272 is a practical accessory when you want to connect the wide ESATTO 3" focuser or ARCO 3" rotator with correctors, reducers or other devices in the M72 standard, while maintaining full back-focus adjustment and the stability of the mechanical connection.