Askar 0.75x Reducer for Askar 91F & ZWO FF90 Apo Telescopes
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Reduces the telescope’s focal ratio to f/5 for a wider field and faster imaging.
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Triplet optical design with a 44 mm full‑frame image circle for edge‑to‑edge sharpness.
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55 mm backfocus and threaded connections for easy integration.
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CNC‑machined construction with metal caps and built‑in filter thread.
Askar 91F 0.75x Reducer: Enhance your Imaging Experience!
Introducing the Askar 0.75x reducer for 91F refractors designed to enhance your astrophotography by providing a faster focal ratio and wider field of view! Featuring a triplet lens design for a flatter, more evenly illuminated image—making it easier to capture large nebulae, star clusters, and other deep-sky objects. With a thoughtful design for easy integration with thoughtful features like built-in filter threads and protective caps. This Askar reducer simplifies your setup while maintaining high-quality performance.
This reducer supports a 44 mm full-frame image circle, with a standard back focus of 55 mm (measured from the M48 thread), with M59x1 threads on both ends for easy compatibility! The included 91F extension tube offers both M54x0.75 and M48x0.75 adapters, allowing direct connection to the 0.75x reducer. Threaded for directly threading a 2-inch filter, eliminating the need for more adapters in your imaging train. Constructed using CNC machining, the reducer boasts a great finish and comes with front and rear metal thread caps for dust protection during storage.
Spot Diagram
Path Optical Diagram
Structrual Diagram
Installation Diagram
Specifications
- (After attaching) 60F Focal length: 455 mn
- (After attaching) 60F Focal ratio: f/5
- Lens Number: Triplet design
- Back Focus: 55 mm (from the base of M48 male thread）
- Weight: 0.3 kg (0.66 lb)
- Rear-end thread type: M59x1
Other Information
- Country of Manufacture: China
Askar 91F 0.75x Reducer: Enhance your Imaging Experience!
Introducing the Askar 0.75x reducer for 91F refractors designed to enhance your astrophotography by providing a faster focal ratio and wider field of view! Featuring a triplet lens design for a flatter, more evenly illuminated image—making it easier to capture large nebulae, star clusters, and other deep-sky objects. With a thoughtful design for easy integration with thoughtful features like built-in filter threads and protective caps. This Askar reducer simplifies your setup while maintaining high-quality performance.
This reducer supports a 44 mm full-frame image circle, with a standard back focus of 55 mm (measured from the M48 thread), with M59x1 threads on both ends for easy compatibility! The included 91F extension tube offers both M54x0.75 and M48x0.75 adapters, allowing direct connection to the 0.75x reducer. Threaded for directly threading a 2-inch filter, eliminating the need for more adapters in your imaging train. Constructed using CNC machining, the reducer boasts a great finish and comes with front and rear metal thread caps for dust protection during storage.
Spot Diagram
Path Optical Diagram
Structrual Diagram
Installation Diagram
Specifications
- (After attaching) 60F Focal length: 455 mn
- (After attaching) 60F Focal ratio: f/5
- Lens Number: Triplet design
- Back Focus: 55 mm (from the base of M48 male thread）
- Weight: 0.3 kg (0.66 lb)
- Rear-end thread type: M59x1
- 0.75x reducer
- Photographic extension tube
- M54x0.75 adapter
- M48x0.75 adapter
- 2x threaded metal dust caps
-
Reduces the telescope’s focal ratio to f/5 for a wider field and faster imaging.
-
Triplet optical design with a 44 mm full‑frame image circle for edge‑to‑edge sharpness.
-
55 mm backfocus and threaded connections for easy integration.
-
CNC‑machined construction with metal caps and built‑in filter thread.
Askar 91F 0.75x Reducer: Enhance your Imaging Experience!
Introducing the Askar 0.75x reducer for 91F refractors designed to enhance your astrophotography by providing a faster focal ratio and wider field of view! Featuring a triplet lens design for a flatter, more evenly illuminated image—making it easier to capture large nebulae, star clusters, and other deep-sky objects. With a thoughtful design for easy integration with thoughtful features like built-in filter threads and protective caps. This Askar reducer simplifies your setup while maintaining high-quality performance.
This reducer supports a 44 mm full-frame image circle, with a standard back focus of 55 mm (measured from the M48 thread), with M59x1 threads on both ends for easy compatibility! The included 91F extension tube offers both M54x0.75 and M48x0.75 adapters, allowing direct connection to the 0.75x reducer. Threaded for directly threading a 2-inch filter, eliminating the need for more adapters in your imaging train. Constructed using CNC machining, the reducer boasts a great finish and comes with front and rear metal thread caps for dust protection during storage.
Spot Diagram
Path Optical Diagram
Structrual Diagram
Installation Diagram
Specifications
- (After attaching) 60F Focal length: 455 mn
- (After attaching) 60F Focal ratio: f/5
- Lens Number: Triplet design
- Back Focus: 55 mm (from the base of M48 male thread）
- Weight: 0.3 kg (0.66 lb)
- Rear-end thread type: M59x1
Other Information
- Country of Manufacture: China
- 0.75x reducer
- Photographic extension tube
- M54x0.75 adapter
- M48x0.75 adapter
- 2x threaded metal dust caps
Askar 0.75x Reducer for Askar 91F & ZWO FF90 Apo Telescopes