Type: Monocular — precision secondary mirror assembly for astronomical use Key benefits Precise optical mount dimensions for reliable alignment and consistent image quality during observing and imaging. Designed to accept common telescope accessories so you can quickly add magnification, contrast filters, or imaging adapters without custom modification. Small, specific dimensions make it straightforward to check compatibility with your focuser, diagonal, or secondary mount. Specifications (exact) Secondary mirror minor axis: about 19 mm Secondary mirror major axis: about 27 mm Secondary mirror seat height: 39 mm Secondary mirror mount diameter: 22 mm Thread bottom diameter: about 4.3 mm Product type: Monocular / secondary mirror assembly for astronomical applications Function & compatibility Intended as an optical component for astronomical telescopes and monocular setups; integrates with standard accessory chains. Compatible with Barlow lenses (2x, 3x), moon filters, and planetary filters to enhance detail and contrast on the Moon, planets, and bright deepsky targets. Designed to work with astrophotography and imaging accessories: Tring adapters, primefocus adapters, field flatteners, focal reducers, smartphone adapters, and dedicated astronomy cameras. Performance advantages Correctly sized mirror and seat height help preserve collimation and focal geometry for sharper planetary and lunar detail. Thread and mount diameters documented so you can confirm mechanical fit before buying additional adapters or cameras. Enables modular upgrades: add a Barlow for higher magnification, filters for contrast control, or a Tring/primefocus adapter for direct imaging. Use scenarios Lunar and planetary observing: Install a 2x or 3x Barlow and a moon or planetary filter to increase magnification and reduce glare for clearer craters and cloud bands. Backyard astrophotography: Attach a primefocus adapter or Tring plus a dedicated astronomy camera to capture images of planets and the Moon with minimal reconfiguration. Quick field demonstrations: Use a smartphone adapter with this assembly to share live views of the Moon or bright planets during outreach or teaching sessions. What to check before use Confirm your focuser/diagonal accepts a 22 mm mount diameter and that the 39 mm seat height suits your optical train. Verify the thread bottom diameter (about 4.3 mm) if you plan to use threaded adapters or retaining hardware. This product provides precise secondary mirror dimensions and standard accessory compatibility to help you expand observing or imaging capability while keeping setup predictable and repeatable.