ASKAR REFRACTOR SQA130 PETZVAL

ASKAR REFRACTOR SQA130 PETZVAL

AIR SPACED SD GLASS QUINTUPLET PETZVAL ASTROGRAPH

Technical Specifications

• Petzval quintuplet astrograph with air-spaced lens design
• Two SD glass elements
• Supports medium format imaging
• Central RMS star spot < 2 µm
• RMS star spot at 55 mm < 2.4 µm
• Relative illumination > 95% at 44 mm
• Relative illumination > 85% at 55 mm
• Self-corrected optical system — no external flattener required
• Effective connection distance: 46–76 mm
• Retractable dew shield
• Lightweight dual tube rings with hollow centre section
• Large manual clamp screws for tool-free operation
• Dual M4/M6 mounting threads on both sides supporting secondary OTA
• Handle slot compatible with multifunction finder accessories
• 300 mm Losmandy-style dovetail plate
• Dual finder bases on focuser sides
• High-precision 360° rotator with engraved scale and large locking screw
• Rigid dual-speed 3.2" rack-and-pinion focuser compatible with motor units
• 30 mm focusing travel
• CNC machined focuser with internal anti-reflection structure and matte coating
• CNC tube machining with anodised finish and exclusive plates
• Rear M68 → M54 → M48 step adapter
• Compatible with astronomy cameras, mirrorless and DSLR systems
• MTF performance > 0.9 at 10 LP/mm
• Central spot < 2 µm, edge spot < 2.4 µm
• ZYGO interferometer test confirms excellent stellar imaging quality

EXCEPTIONAL PERFORMANCE

Air spaced quintuplet optical design including two pieces of SD glass.
The SQA130 supports medium format imaging.
The central star point shows an RMS radius of less than two microns, and the star point at fifty five millimetres is less than two point four microns, demonstrating remarkable star fineness.
It also delivers excellent full field illumination and outstanding MTF values.
Relative illumination can exceed ninety five percent at forty four millimetres and above eighty five percent at fifty five millimetres.

PETZVAL STRUCTURE

Integrated self corrected optical system eliminating the need for an additional flattener and simplifying back focus requirements.
With a connection distance between forty six and seventy six millimetres, users can directly use it for imaging once the OTA is focused.

RETRACTABLE DEW SHIELD

The dew shield adopts a retractable design that can be extended.
It protects the objective from external and internal light impact and also safeguards the front lens from collision.

INTEGRATED TUBE RING

Lightweight dual tube ring design with a hollowed centre section to reduce weight.
Large hand screws allow opening and closing without additional tools.
Six M4 and M6 threaded holes on both sides allow flexible installation of various bases, even supporting a secondary telescope for imaging.
The handle features a slot compatible with a multifunctional finder base, enabling attachment of a wide range of astronomical accessories.

PLATINE EN QUEUE D’ARONDE

Platine en queue d’aronde de trois cents millimètres de type Losmandy, assurant une installation fluide, sécurisée et facile.

DUAL FINDER BASES

Both sides of the focuser are equipped with finder bases, allowing flexible mounting without repeated disassembly.
They are also suitable for attaching additional astronomical accessories.

THREE HUNDRED AND SIXTY DEGREE ROTATOR

The rear of the focuser is equipped with a high precision three hundred and sixty degree rotator featuring a scale to set and store the rotation angle.
It also includes a large locking screw for easy secure clamping even under heavy load.

LARGE RIGID DUAL SPEED FOCUSER

Rigid dual speed three point two inch rack and pinion focuser compatible with most motorised focusers on the market.
The focusing travel is thirty millimetres and the focuser tube is engraved with high precision scales.
The entire focuser assembly is CNC machined with an internal anti reflective structure and matte coating providing additional measures to eliminate stray light.

HIGH QUALITY MACHINING

The entire SQA130 tube is manufactured using high quality CNC machining with anodising and sprayed surface coating.
Exclusive nameplates are embedded on the handle and focuser for a high end finish.

REAR ADAPTERS

The rear of the SQA130 includes an M sixty eight to M fifty four to M forty eight step adapter allowing secure and easy connection to various imaging devices such as full frame cameras.

MULTI PLATFORM COMPATIBILITY

Compatible with professional astronomy cameras.
It also works with mirrorless and DSLR cameras using appropriate adapters.

OPTICAL PATH

The SQA130 adopts an air spaced quintuplet optical structure including two pieces of SD glass.

MTF CHART

The modulation transfer function is a quantitative measurement of optical image clarity including resolution and contrast.
The vertical axis represents the MTF value and the horizontal axis indicates the distance from centre to edge.
In both low and high frequency curve sets, even at the fifty five millimetre image circle edge, the difference between sagittal and meridional lines remains very small.
At low frequency ten LP per millimetre, the overall value remains above zero point nine demonstrating the high resolution and sharpness of the SQA130.

RELATIVE ILLUMINATION

Relative illumination represents the combined effect of light loss and corner attenuation.
The RI curve illustrates brightness variation in percentage across the sensor area.
Illumination variations can affect the image.
The vertical axis represents illumination percentages while the horizontal axis indicates distance from frame centre to edge.
The SQA130 achieves more than ninety five percent illumination at the edge of a forty four millimetre image circle and more than eighty five percent at fifty five millimetres.
This demonstrates effective control of vignetting and field curvature enabling high quality images with uniform brightness from centre to edge even with large sensors.

SPOT DIAGRAM

Image quality can be evaluated by analysing spot distribution on the spot diagram.
The SQA130 demonstrates exceptionally fine stellar performance with a central star RMS radius below two microns and a star spot radius below two point four microns at the edge of the fifty five millimetre image circle reflecting excellent aberration correction capability.

ZYGO OBJECTIVE CHART

The ZYGO interferometer is internationally recognised as an authoritative instrument for testing optical quality and SQA130 test results show excellent star image performance.