The M81 → M57 adapter with stop ring for ESATTO 3" / ARCO 3" (PrimaLuceLab, SKU: PL3600279 ) enables the connection of M57 × 1 threaded accessories (e.g. filter wheel, planetary cameras, extensions) 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 makes it easier to maintain the correct back-focus and orientation of the connected accessory.
• thread conversion: input M81 × 1 (ESATTO 3" / ARCO 3") → output M57 × 1
• stop ring – precise position adjustment and secure adapter lock
• optical thickness of only 7 mm – negligible impact on the back-focus budget
• internal grooving and black anodizing – effective reflection reduction
• CNC milled body made of 6061-T6 aluminum – lightness, stiffness, corrosion resistance
• M81 → M57 adapter with stop ring
• Ring locking screw (Allen key)
• input thread: M81 × 1 (female)
• output thread: M57 × 1 (male)
• optical length: 7 mm
• Inner diameter: 57 mm
• material: aluminum 6061-T6, black anodized
• compatibility: ESATTO 3" lift, ARCO 3" rotator, accessories with M57 × 1 thread
• EAN: 8059020773267
• manufacturer: PrimaLuceLab – Italy
PL3600279 is a practical accessory wherever you want to connect a wide ESATTO 3" extension arm or an ARCO 3" rotator with a camera or other device in the M57 standard, while maintaining full back-focus adjustment and the stability of a mechanical connection.
