Askar 91F 91mm f/6.7 Quadruplet Flat-Field Refractor Telescope
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- Excellent quality affordable refractor for astrophotography
- 91mm aperture and f/6.7 focal ratio
- Quadruplet air-spaced APO design with ED glass
- Built-in field flattening optical design
- Supports full-frame sensors
- Dual-speed 2.4" focuser - electronic focuser compatible
- Multiple rear thread options (M64, M54, M48)
Askar 91F: Ready for the Road, Built for the Stars!
Manufactured by Sharpstar Optics, the Askar 91F Flat-Field Quadruplet Astrograph is the ultimate versatile scope—just as skilled at showing you the stars through an eyepiece as it is at locking onto them with a camera sensor! Packing a versatile 91mm aperture, 609mm focal length, and a native f/6.7 focal ratio, this optical powerhouse boasts a clever 4-element design (three up front, one in the back) featuring premium ED glass. What does that mean for you? It means chromatic aberration gets kicked to the curb. Best of all, thanks to its built-in self-flattening wizardry, it serves up a gorgeous, pin-sharp 44mm full-frame image circle—giving you perfectly round star points right to the very edge of your shot, zero back spacing math required!
Popular Astrophotography YouTuber Naztronomy reviews the Askar 91F!
Askar 91F Standout Features
Flat-Field Built-in
The optical design of the Askar 91F features a four-element configuration (three elements in the front and one in the rear), including one piece of ED glass， which can effectively reduce chromatic aberration.The Askar 91F supports 44mm full-frame imaging with great performance of the surrounding star points.
Versatile and Portable
The Askar 91F strikes a balance between practicality and versatility while achieving lightweight portability through its compact design.The OTA weighs just 3.92kgs (8.5 lbs). Versatile allowing both visual observation and astrophotography, the 91F comes standard with an 8mm and 20mm eyepiece, as well as a 1.25" erecting prism.
Included Camera Adapters
The Askar 91F also comes standard with a photographic extension tube with a built-in 2-inch filter thread for easy shooting connections, providing M48x0.75 & M54x.075 adapters to accommodate various DSLR cameras and professional astronomical cameras, meeting diverse imaging needs.
Built with Purpose
A generous 130mm (5.12") handle features a built-in finder base slot, complemented by two additional finder bases integrated directly onto either side of the focuser so you never have to unscrew and re-mount your gear when swapping sides. For rock-solid precision, the 91F relies on a heavy-duty 3-inch dual-speed Rack & Pinion focuser featuring an ultra-smooth 1:10 fine-adjustment knob and a 360° scaled rotator for dead-accurate framing. Supporting the entire rig is a 230mm (9.06") Vixen-style dovetail plate natively drilled with 1/4" and 3/8" screw holes, letting you lock this stunning CNC-machined powerhouse onto a standard photo tripod just as easily as an equatorial tracker.
Ready for Visual Observation
The package includes two 1.25" eyepieces, each equipped with a soft rubber guard for comfortable viewing. The 20mm eyepiece provides 30x magnification, while the 8mm eyepiece steps it up to 76x. While the Askar 91F can easily pair with various eyepieces depending on your target, both included options are absolutely ideal for tracking birds and scanning landscapes. The included 1.25" erecting prism corrects your view both horizontally and vertically. This gives you a natural, properly oriented image, allowing you to transition between terrestrial and astronomical observations without the headache of a flipped or mirrored perspective.
Perfect Tool for the Versatile Astronomer
The Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flatteners. After attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of shooting. (Mounts and Tripods not included, only for display purposes)
The Full 91F Rundown
Specifications
- Aperture size: 91 mm
- Focal length: 609 mm
- Focal ratio: f/6.7
- Objective lens: Quadruplet air-spaced APO (including one ED glass)
- Image circle: 44mm
- Focuser travel length: 30mm
- Maximum accessory connection (with the focuser fully retreated):
- Imaging mode:
- 75mm (from the base of M48x0.75 male thread)
- 93mm (from the base of M54x0.75 male thread)
- Observing mode:
- 112mm (from the end of 1.25" eyepiece holder)
- 122mm (from the end of 2" eyepiece holder)
- Imaging mode:
- Total length:
- 513mm (including 1.25" adapter as dew shield contracted)
- 599mm (including 1.25" adapter as dew shield fully stretched)
- 550mm (including the photographic adapter as dew shield contracted)
- 636mm (including the photographic adapter as dew shield fully stretched)
- Net weight: 3.92 kg (8.7 lb)
- Gross weight (Including tube ring&dovetail plate): 4.52 kg (10 lb)
- Rear-end thread type:
- M64x0.75-M54x0.75
- M54x0.75-M54x0.75
- M54x0.75-M48x0.75 (with M48x0.75 filter thread)
Mechanical Diagrams
Product Size Diagram
Camera Connection
Electronic Focuser Assembly Diagram
Optical Test Charts
Optical Path Diagram
Spot Diagram
Locking Screw Position
Other Information
- Country of Manufacture: China
Askar 91F: Ready for the Road, Built for the Stars!
Manufactured by Sharpstar Optics, the Askar 91F Flat-Field Quadruplet Astrograph is the ultimate versatile scope—just as skilled at showing you the stars through an eyepiece as it is at locking onto them with a camera sensor! Packing a versatile 91mm aperture, 609mm focal length, and a native f/6.7 focal ratio, this optical powerhouse boasts a clever 4-element design (three up front, one in the back) featuring premium ED glass. What does that mean for you? It means chromatic aberration gets kicked to the curb. Best of all, thanks to its built-in self-flattening wizardry, it serves up a gorgeous, pin-sharp 44mm full-frame image circle—giving you perfectly round star points right to the very edge of your shot, zero back spacing math required!
Popular Astrophotography YouTuber Naztronomy reviews the Askar 91F!
Askar 91F Standout Features
Flat-Field Built-in
The optical design of the Askar 91F features a four-element configuration (three elements in the front and one in the rear), including one piece of ED glass， which can effectively reduce chromatic aberration.The Askar 91F supports 44mm full-frame imaging with great performance of the surrounding star points.
Versatile and Portable
The Askar 91F strikes a balance between practicality and versatility while achieving lightweight portability through its compact design.The OTA weighs just 3.92kgs (8.5 lbs). Versatile allowing both visual observation and astrophotography, the 91F comes standard with an 8mm and 20mm eyepiece, as well as a 1.25" erecting prism.
Included Camera Adapters
The Askar 91F also comes standard with a photographic extension tube with a built-in 2-inch filter thread for easy shooting connections, providing M48x0.75 & M54x.075 adapters to accommodate various DSLR cameras and professional astronomical cameras, meeting diverse imaging needs.
Built with Purpose
A generous 130mm (5.12") handle features a built-in finder base slot, complemented by two additional finder bases integrated directly onto either side of the focuser so you never have to unscrew and re-mount your gear when swapping sides. For rock-solid precision, the 91F relies on a heavy-duty 3-inch dual-speed Rack & Pinion focuser featuring an ultra-smooth 1:10 fine-adjustment knob and a 360° scaled rotator for dead-accurate framing. Supporting the entire rig is a 230mm (9.06") Vixen-style dovetail plate natively drilled with 1/4" and 3/8" screw holes, letting you lock this stunning CNC-machined powerhouse onto a standard photo tripod just as easily as an equatorial tracker.
Ready for Visual Observation
The package includes two 1.25" eyepieces, each equipped with a soft rubber guard for comfortable viewing. The 20mm eyepiece provides 30x magnification, while the 8mm eyepiece steps it up to 76x. While the Askar 91F can easily pair with various eyepieces depending on your target, both included options are absolutely ideal for tracking birds and scanning landscapes. The included 1.25" erecting prism corrects your view both horizontally and vertically. This gives you a natural, properly oriented image, allowing you to transition between terrestrial and astronomical observations without the headache of a flipped or mirrored perspective.
Perfect Tool for the Versatile Astronomer
The Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flatteners. After attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of shooting. (Mounts and Tripods not included, only for display purposes)
The Full 91F Rundown
Specifications
- Aperture size: 91 mm
- Focal length: 609 mm
- Focal ratio: f/6.7
- Objective lens: Quadruplet air-spaced APO (including one ED glass)
- Image circle: 44mm
- Focuser travel length: 30mm
- Maximum accessory connection (with the focuser fully retreated):
- Imaging mode:
- 75mm (from the base of M48x0.75 male thread)
- 93mm (from the base of M54x0.75 male thread)
- Observing mode:
- 112mm (from the end of 1.25" eyepiece holder)
- 122mm (from the end of 2" eyepiece holder)
- Imaging mode:
- Total length:
- 513mm (including 1.25" adapter as dew shield contracted)
- 599mm (including 1.25" adapter as dew shield fully stretched)
- 550mm (including the photographic adapter as dew shield contracted)
- 636mm (including the photographic adapter as dew shield fully stretched)
- Net weight: 3.92 kg (8.7 lb)
- Gross weight (Including tube ring&dovetail plate): 4.52 kg (10 lb)
- Rear-end thread type:
- M64x0.75-M54x0.75
- M54x0.75-M54x0.75
- M54x0.75-M48x0.75 (with M48x0.75 filter thread)
Mechanical Diagrams
Product Size Diagram
Camera Connection
Electronic Focuser Assembly Diagram
Optical Test Charts
Optical Path Diagram
Spot Diagram
Locking Screw Position
| Manufacturer | Askar |
|---|---|
| Telescope Focal Length | 601 - 700mm |
- 1x 91F OTA
- 1x Tube rings
- 1x Handle
- 1x 230mm Vixen dovetail plate
- 1x Set of photographic adapters
- 1x 1.25" 45° erecting prism
- 1x 8mm eyepiece
- 1x 20mm eyepiece
- Excellent quality affordable refractor for astrophotography
- 91mm aperture and f/6.7 focal ratio
- Quadruplet air-spaced APO design with ED glass
- Built-in field flattening optical design
- Supports full-frame sensors
- Dual-speed 2.4" focuser - electronic focuser compatible
- Multiple rear thread options (M64, M54, M48)
Askar 91F: Ready for the Road, Built for the Stars!
Manufactured by Sharpstar Optics, the Askar 91F Flat-Field Quadruplet Astrograph is the ultimate versatile scope—just as skilled at showing you the stars through an eyepiece as it is at locking onto them with a camera sensor! Packing a versatile 91mm aperture, 609mm focal length, and a native f/6.7 focal ratio, this optical powerhouse boasts a clever 4-element design (three up front, one in the back) featuring premium ED glass. What does that mean for you? It means chromatic aberration gets kicked to the curb. Best of all, thanks to its built-in self-flattening wizardry, it serves up a gorgeous, pin-sharp 44mm full-frame image circle—giving you perfectly round star points right to the very edge of your shot, zero back spacing math required!
Popular Astrophotography YouTuber Naztronomy reviews the Askar 91F!
Askar 91F Standout Features
Flat-Field Built-in
The optical design of the Askar 91F features a four-element configuration (three elements in the front and one in the rear), including one piece of ED glass， which can effectively reduce chromatic aberration.The Askar 91F supports 44mm full-frame imaging with great performance of the surrounding star points.
Versatile and Portable
The Askar 91F strikes a balance between practicality and versatility while achieving lightweight portability through its compact design.The OTA weighs just 3.92kgs (8.5 lbs). Versatile allowing both visual observation and astrophotography, the 91F comes standard with an 8mm and 20mm eyepiece, as well as a 1.25" erecting prism.
Included Camera Adapters
The Askar 91F also comes standard with a photographic extension tube with a built-in 2-inch filter thread for easy shooting connections, providing M48x0.75 & M54x.075 adapters to accommodate various DSLR cameras and professional astronomical cameras, meeting diverse imaging needs.
Built with Purpose
A generous 130mm (5.12") handle features a built-in finder base slot, complemented by two additional finder bases integrated directly onto either side of the focuser so you never have to unscrew and re-mount your gear when swapping sides. For rock-solid precision, the 91F relies on a heavy-duty 3-inch dual-speed Rack & Pinion focuser featuring an ultra-smooth 1:10 fine-adjustment knob and a 360° scaled rotator for dead-accurate framing. Supporting the entire rig is a 230mm (9.06") Vixen-style dovetail plate natively drilled with 1/4" and 3/8" screw holes, letting you lock this stunning CNC-machined powerhouse onto a standard photo tripod just as easily as an equatorial tracker.
Ready for Visual Observation
The package includes two 1.25" eyepieces, each equipped with a soft rubber guard for comfortable viewing. The 20mm eyepiece provides 30x magnification, while the 8mm eyepiece steps it up to 76x. While the Askar 91F can easily pair with various eyepieces depending on your target, both included options are absolutely ideal for tracking birds and scanning landscapes. The included 1.25" erecting prism corrects your view both horizontally and vertically. This gives you a natural, properly oriented image, allowing you to transition between terrestrial and astronomical observations without the headache of a flipped or mirrored perspective.
Perfect Tool for the Versatile Astronomer
The Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flatteners. After attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of shooting. (Mounts and Tripods not included, only for display purposes)
The Full 91F Rundown
Specifications
- Aperture size: 91 mm
- Focal length: 609 mm
- Focal ratio: f/6.7
- Objective lens: Quadruplet air-spaced APO (including one ED glass)
- Image circle: 44mm
- Focuser travel length: 30mm
- Maximum accessory connection (with the focuser fully retreated):
- Imaging mode:
- 75mm (from the base of M48x0.75 male thread)
- 93mm (from the base of M54x0.75 male thread)
- Observing mode:
- 112mm (from the end of 1.25" eyepiece holder)
- 122mm (from the end of 2" eyepiece holder)
- Imaging mode:
- Total length:
- 513mm (including 1.25" adapter as dew shield contracted)
- 599mm (including 1.25" adapter as dew shield fully stretched)
- 550mm (including the photographic adapter as dew shield contracted)
- 636mm (including the photographic adapter as dew shield fully stretched)
- Net weight: 3.92 kg (8.7 lb)
- Gross weight (Including tube ring&dovetail plate): 4.52 kg (10 lb)
- Rear-end thread type:
- M64x0.75-M54x0.75
- M54x0.75-M54x0.75
- M54x0.75-M48x0.75 (with M48x0.75 filter thread)
Mechanical Diagrams
Product Size Diagram
Camera Connection
Electronic Focuser Assembly Diagram
Optical Test Charts
Optical Path Diagram
Spot Diagram
Locking Screw Position
Other Information
- Country of Manufacture: China
| Manufacturer | Askar |
|---|---|
| Telescope Focal Length | 601 - 700mm |
- 1x 91F OTA
- 1x Tube rings
- 1x Handle
- 1x 230mm Vixen dovetail plate
- 1x Set of photographic adapters
- 1x 1.25" 45° erecting prism
- 1x 8mm eyepiece
- 1x 20mm eyepiece
Askar 91F 91mm f/6.7 Quadruplet Flat-Field Refractor Telescope