Askar 71F Flat Field launches from SharpStar Optics

The Askar 71F Flat-Field is an optical tube assembly (OTA) characterized by a 71mm aperture, 490mm focal length, and an inherent focal ratio of F6.9.

This model features a quadruplet air-spaced APO lens arrangement, incorporating a single ED glass element to significantly minimize chromatic aberration. It is optimized for 44mm full-frame imaging, delivering excellent clarity and detail in star point representations.

Askar 71F can be used for both visual observation and astrophotography

Designed for simplicity, the Askar 71F eliminates the need for a separate field flattener and back-focus calculations. Once imaging accessories are attached, the OTA can be used immediately for photography, enhancing both cost efficiency and user enjoyment.

Key features of the Askar 71F Flat-Field from SharpStar Optics

• Aperture and Focal Length: The Askar 71F features a 71mm aperture, 490mm focal length, and a focal ratio of F6.9, suitable for both visual observation and astrophotography.
• Lens Design: Utilizes a quadruplet air-spaced APO lens configuration with one piece of ED glass to support 44mm full-frame imaging.
• Self-Flattened Design: Designed to operate without the need for backfocus calculations, allowing immediate use after attachment of imaging accessories.
• Weight and Dimensions: The optical tube assembly weighs 2.5kg, with a total weight of 3kg including tube rings and dovetail plate.
• Included Accessories: Comes with a 25x 8mm eyepiece, a 60x 20mm eyepiece, and a 1.25-inch erecting prism.
• Photographic Extensions: Includes a photographic extension tube with M480.75 & M540.75 adapters and a built-in 2-inch filter thread.
• Retractable Dew Shield: Features a retractable dew shield for enhanced portability and reduced stray light reflections, crafted from CNC-machined materials.
• Finder Bases: Equipped with a finder base on the handle and two on the sides of the focuser, providing flexibility and additional mounting options without needing to disassemble.
• Focuser Features: Sports a dual-speed 2.4-inch R&P focuser with 1:10 fine adjustment and a 360° rotatable scale field for precise angle adjustments.
• Mounting Options: The 230mm standard Vixen dovetail plate includes slots for both 1/4 and 3/8 screw holes, allowing for direct tripod attachment.
   

Technical specifications of the Askar 71F:

Aperture size: 71mm

Focal length: 490mm

Focal ratio: f/6.9

Objective lens: Quadruplet air-spaced APO(including one ED glass)

Image circle: 44mm

Maximum accessory connection (with the focuser fully retreated)

• Imaging mode:
82.5mm (from the base of M48×0.75 male thread）
100.5mm（from the base of M54×0.75 male thread)
• Observing mode:
117mm（from the end of 1.25" eyepiece holder）
127mm（from the end of 2" eyepiece holder)
   

Total length:

• 372.5mm(including 1.25" adapter as dew shield contracted）
• 430.9mm(including 1.25" adapter as dew shield fully stretched）
• 415mm(including the photographic adapter as dew shield contracted）
• 473.4mm(including the photographic adapter as dew shield fully stretched)
   

Net weight: 2.5kg

Gross weight (Including tube ring&dovetail plate): 3.0kg

Rear-end thread type: M64×0.75-M54×0.75
M54×0.75-M54×0.75
M54×0.75-M48×0.75 (with M48×0.75 filter thread)

Standard package items: A 71F OTA, a pair of tube rings, a handle, a Vixen 230mm dovetail plate, a set of photographic adapters, a 1.25" 45° erecting prism, an 8mm eyepiece, a 20mm eyepiece

The 71F supports 44mm full-frame imaging