ASKAR REFRACTOR SQA70 PRO PETZVAL

High-Performance Petzval Optics

The Askar SQA70 Pro features a six-element, air-spaced Petzval apochromatic optical design incorporating one SD glass element and one ED glass element.

This configuration provides effective correction of chromatic aberrations and field curvature without requiring an additional field flattener.

With a 322 mm focal length and a fast f/4.6 focal ratio, this refractor is particularly well suited for wide-field imaging of nebulae and other deep-sky objects.

Mechanical Design and Versatility

A 2.5-inch Rack & Pinion focuser, a graduated 360° rotator, and M42, M48, and M54 interfaces make it easy to integrate different imaging accessories.

The multifunctional tube rings, 290 mm Vixen-style dovetail plate, and dual finder bases allow the telescope to accommodate a wide range of imaging configurations.

Detailed Technical Specifications

Optical System

• Optical design: Petzval apochromatic
• Number of elements: 6 air-spaced lenses
• Special glass elements: 1 SD element and 1 ED element
• Aperture: 70 mm
• Focal length: 322 mm
• Focal ratio: f/4.6
• Sensor compatibility: Full-frame, up to 44 mm diagonal
• Field curvature correction: Integrated
• Additional field flattener: Not required
• Rear connection distance: 36 to 68 mm
• Recommended connection distance: 55 mm

Optical Performance

• RMS spot radius at field center: Less than 0.75 µm
• RMS spot radius at field corners: Less than 1.24 µm
• Relative illumination at full-frame edges: Above 95%
• Chromatic correction: SD and ED glass elements
• Longitudinal chromatic aberration: Highly corrected

Focuser and Rotator

• Focuser type: Rack & Pinion
• Diameter: 2.5 inches
• Focusing mechanism: Dual-speed
• Focuser travel: 32 mm
• Drawtube: Graduated scale
• Construction: CNC-machined
• Internal treatment: Grooves and matte black coating
• Motorization: Compatible with most electronic focus motors
• Rotator: 360°
• Angular adjustment: Graduated scale
• Locking mechanism: Knurled locking screw

Connections and Accessories

• Rear interfaces: M42, M48, and M54
• Filter thread: 2-inch on M48 interface
• Tube rings: 2, with hollowed-out design
• Mounting threads: M4 and M6
• Upper handle: Multifunctional mounting support
• Dovetail plate: Vixen-style
• Dovetail length: 290 mm
• Balance markings: Graduated scales on both sides
• Finder bases: 2
• Dew shield: Fixed

OPTICAL SYSTEM INNOVATION

Building on the solid foundation of the original SQA70, the SQA70 Pro features an upgraded six-element air-spaced Petzval optical design. 

While delivering outstanding optical performance, this new design further enhances image stability.

The second lens element uses high-quality SD glass, while the fourth element is made from ED glass. These two premium optical materials effectively correct chromatic aberrations and improve image sharpness.

PETZVAL DESIGN

The Petzval optical design incorporates an integrated field-flattening system compatible with full-frame sensors.

No additional field flattener is required, and no specific backfocus calculations are necessary.

Simply achieve focus with a connection distance between 36 and 68 mm to begin imaging.

FIXED DEW SHIELD

Equipped with a robust fixed dew shield, the telescope provides effective protection against internal and external stray light.

This design also helps protect the optical elements from accidental impacts during everyday use, storage, or transportation, ensuring comprehensive protection for the objective lens.

DOVETAIL PLATE

The telescope features a standard 290 mm Vixen-style dovetail plate, allowing easy installation and removal with smooth and convenient handling.

Both sides of the dovetail plate feature graduated scales, providing a clear visual reference for quickly and accurately determining the instrument's optimal balance point.

INTEGRATED TUBE RINGS

The telescope features two integrated tube rings with hollowed-out central sections to reduce the overall weight of the instrument.

The enlarged knurled locking screws allow quick, tool-free opening and closing for easy and convenient handling.

Each side of the tube rings features two M4 and M6 threaded holes, making it easy to attach mounting brackets, dovetail plates, or even an additional telescope for versatile imaging configurations.

The top handle of the tube rings incorporates a multifunctional mounting slot for attaching various astronomical accessories, offering excellent flexibility for future upgrades and customization.

DUAL FINDER BASES

Each side of the focuser is equipped with a finder base.

This configuration not only allows the finder scope to be removed and reinstalled without repositioning its mounting base, but also provides additional mounting points for other astronomical accessories.

ROBUST LARGE-DIAMETER DUAL-SPEED FOCUSER

The telescope is equipped with a rigid 2.5-inch Rack & Pinion focuser featuring a dual-speed focusing mechanism and compatibility with most electronic focus motors available on the market.

The focuser offers 32 mm of travel, and its drawtube features high-precision graduated markings for accurate and repeatable focusing adjustments.

The entire focuser body is CNC-machined and features internal grooves and a matte black coating, effectively minimizing stray light through multiple levels of internal reflection suppression.

360° ROTATOR

The rear section of the focuser features a robust, high-precision 360° rotator with a graduated scale for accurate and repeatable rotation angle adjustments.

A knurled locking screw ensures a firm and secure hold, even under heavy loads.

ADAPTATEURS ARRIÈRE

L’arrière du SQA70 est équipé de plusieurs adaptateurs dentés et rainurés pour une rotation manuelle aisée sans glissement.
Les adaptateurs sont disponibles en formats M54, M48 et M42, permettant la connexion de divers accessoires tels que des caméras refroidies.

APPLICATIONS PHOTOGRAPHIQUES DIVERSIFIÉES

En plus de pouvoir être relié à une caméra astronomique pour l’astrophotographie, le SQA70 peut également être connecté à un appareil photo hybride ou reflex pour la prise de vue.

Optical Design

The SQA70 Pro features a six-element air-spaced optical design, incorporating one SD glass element and one ED glass element.

Spot Diagram

The image quality of an optical system can be evaluated by analyzing the distribution of light points in the spot diagram.

The SQA70 Pro achieves an RMS spot radius of less than 0.75 µm at the center of the field and less than 1.24 µm in the corners, demonstrating excellent light concentration and outstanding sharpness in stellar images.

Relative Illumination

Relative illumination (RI) represents the combined effect of light loss and brightness falloff toward the edges of the optical field. The RI curve illustrates variations in illumination, expressed as a percentage, across the entire sensor surface.

These brightness variations can affect image uniformity. On the graph, the vertical axis indicates the percentage of relative illumination, while the horizontal axis represents the distance from the center toward the edges of the field.

Even at the edges of a full-frame sensor, the SQA70 Pro maintains relative illumination above 95%, ensuring excellent brightness uniformity across the entire imaging field.

Longitudinal Chromatic Aberration Curve

The longitudinal chromatic aberration curve illustrates variations in the focal point position according to different wavelengths of light. Each curve in the diagram corresponds to a specific wavelength.

Longitudinal chromatic aberration (LCA) occurs when different wavelengths of light do not converge at exactly the same focal point along the optical axis of a refractor or telescope.

This phenomenon can cause focusing differences between colors, often resulting in blurred edges or colored fringes around observed objects.

The longitudinal chromatic aberration curves of the SQA70 Pro show extremely small deviations, with some curves nearly overlapping, as well as remarkably low curvature.

These characteristics demonstrate the SQA70 Pro's excellent correction of longitudinal chromatic aberration and its outstanding optical quality.