The Askar 0.75x reducer for 91F is a dedicated triplet focal reducer designed specifically for the Askar 91F refractor. It reduces the system to a 455 mm focal length at f/5, providing a wider field of view, shorter exposure times, and built-in field-flattening correction for full-frame sensors.

Key features

• reduces the Askar 91F focal length to 455 mm and focal ratio to f/5
• built-in field-flattening correction optimized for astrophotography
• triplet optical design
• supports a 44 mm full-frame image circle
• standard 55 mm back focus from the M48 male thread
• M59 × 1 threads on both ends of the reducer
• compatible with the 91F photographic extension tube with M54 × 0.75 and M48 × 0.75 adapters for direct connection
• built-in M48 × 0.75 internal thread for 2" filters
• CNC-machined body for high mechanical precision
• supplied with front and rear metal threaded caps for protection during storage and transport

Included items

• Askar 0.75x focal reducer for 91F (triplet)
• front threaded metal dust cap
• rear threaded metal dust cap

Technical specifications

• application: focal reducer for Askar 91F refractor
• 91F focal length with reducer: 455 mm
• 91F focal ratio with reducer: f/5
• optical design: triplet
• corrected image circle: 44 mm (full-frame)
• back focus: 55 mm (from the base of the M48 male thread)
• mechanical threads: M59 × 1 (front and rear)
• filter thread: internal M48 × 0.75 (2" filters)
• weight: 0.3 kg
• mechanical construction: CNC-machined, anodized body