Intended for use with with longer-focal-ratio telescopes and eyepieces of narrow to moderately-wide apparent fields of view. Free light transmission - 22.5mm lens aperture. Can be used with additional spacers (available separately) to achieve further focal reduction. Mounting threads - 1.25" filter thread (28.5x0.75MM) on both sides: Threads into eyepieces, camera adapters, and other accessories with standard 1.25" threads, and can be stacked with additional 1.25" threaded accessories. 2 lenses for better correction - cemented together and coated, black-anodized aluminum housing. 85mm focal length, reduction factor of about 0.5X, depending on spacing. 0.5x focal reducer effectively halves the focal length of a telescope, enabling lower magnification, a wider field of view, and shorter exposure times for astrophotography.

Focal Length Description: 85 month. Item Weight: 0.8 Ounces. Finderscope: Reflex. Objective Lens Diameter: 25 Millimeters. Brand: Astromania. Manufacturer: Astromania. Date First Available: January 26, 2016. Is Discontinued By Manufacturer: No. Best Sellers Rank: #42 in Telescope Eyepieces. Customer Reviews: 3.8 out of 5 stars 18 ratings 3.8 out of 5 stars. Item model number: SKU_AM_RC05X. : B01B2OR280. Item Weight: 0.8 ounces. Product Dimensions: 2 x 2 x 0.93 inches.