About this product
Model: askar_sqa70
Part Number: SQA70
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The new Askar SQA 70mm f/4.8 Astrograph features quintuplet air-spaced optics that provide a wide and flat field of view, making it ideal for use with modern large CMOS sensors.
Optical Performance
With a 70mm aperture and a focal length of 336mm, the f/4.8 Quintuplet optics provide a wide, flat field of view over a 44mm imaging circle.
The optical design includes two ED glass elements, and the on-axis star point has a radius of 1.184um. Even at the edge of a 44mm circle, the star point only rises to 2.4um.
The SQA70 also has excellent full-field illumination and MTF Data.
Petzval Optical Design
The SQA70 features an integrated field flattener, so there is no need for an additional field flattener or complex back-focus distance calculations.
With a working back focus of 37mm to 68mm, the SQA 70 can accommodate most imaging/camera combinations. All the user needs to do is attach the camera and focus the telescope.
Integrated Tube Ring
An integrated pair of tube rings with a hollowed design is included to save weight. Enlarged hand screws allow users to open and close the tube rings quickly and easily.
On both sides of the rings, there are four M4 and M6 threaded holes for installing dovetail plates and other accessories.
The handle on the top of the rings is slotted for mounting a finder scope or Finder/Guidescope.
Finder Bases
On both sides of the focuser, there are two finder bases, which not only eliminate disassembling when changing the position of the Finderscope but also provide additional mounting options for other accessories.
Dual-Speed R&P Focuser
The dual-speed Rack & Pinion 2.5" focuser is compatible with most motor focusers on the market. The focus travel is 32mm, and the drawtube is engraved with high-precision scales.
The entire focuser barrel is CNC machined with an anti-reflective internal design to prevent stray light.
360-Degree Rotator
The rear of the Focuser is equipped with a 360-degree high-precision rotator with a precision scale, enabling the user to adjust and save the rotation angle.
It is also equipped with a locking screw for easy locking.
High-Quality Machining
The entire SQA70 tube is crafted using high-quality CNC machining with anodised and surface spray paint treatments. The top of the focuser and handle are designed with exclusive nameplates, demonstrating high-end quality.
Rear Adapters
The rear of the SQA70 accepts various included adapters, all of which are toothed and ribbed, making them easy to rotate manually without slipping. The adapters are available in sizes M54, M48, and M42 and can be used to attach various accessories, including cooled imaging cameras.
Daytime Photography
The SQA70 can also be used with a commercial mirrorless camera for daytime photography.
Dimensions
Optical Path
The SQA70 is a Quintuplet air-spaced Petzval design that includes two ED glass elements.
MTF Chart
The modulation transfer function (MTF) is a quantitative description of the clarity of the image (including resolution and contrast) of an optical lens. The vertical axis is the MTF value, and the horizontal axis is the distance from the centre of the frame to the edge.
In the two sets of curves corresponding to low and high frequencies, even at the edge of the 55mm image circle, the sagittal lines and sagittal lines distance of the SQA70 lens remain very small. The low frequency of 10LP/mm is higher than 0.9 overall, showing the SQA70’s high resolution and sharpness.
Relative illumination
Relative Illumination (RI) represents the combined effect of light loss and attenuation at the corners of the lens.
The RI curve illustrates the change in illuminance (%) across the sensor’s imaging range. Illumination variations can adversely affect the image.
The vertical axis means different percentages of example illumination intensities, and the horizontal axis is the distance from the centre of the frame to the edge.
The SQA70 guarantees a high illumination above 90% at the 44 mm image circle, minimising the vignetting.
Spot Diagram
The imaging quality of the optical system can be evaluated by analysing the distribution of spots on this spot diagram.
The SQA70 has a central star point with an RMS radius of less than 1.84 um, and the star point at the corner is less than 2.4 um, showing a fine star point.
Longitudinal Chromatic Aberration
This chart represents the deviation of different wavelengths of light at the focal point. The curves in the diagram correspond to different wavelengths of light.
Longitudinal chromatic aberration (LCA) occurs when different wavelengths (colours) of light fail to converge at the same focal point along the optical axis of a lens or telescope. Resulting in inconsistent colours in the image, usually manifested as blurred edges or colour separation.
The longitudinal chromatic curves of SQA70 lenses show very small spacing and even coincide. The curve curvature is very low, indicating that the chromatic aberration control ability of the SQA70 lens is very good.
Specifications
| Aperture | 70 mm |
| Focal Length | 336 mm |
| Focal Ratio | f/4.8 |
| Optical Design | Quintuplet (four elements) Petzval APO (includes two ED glass elements) |
| Total Length | 332 mm (dew shield contracted)
372 mm (dew shield extended) |
| Format | Full Frame (44mm imaging circle) |
| OTA Weight | 2.68 kg |
| Gross weight（including tube ring and dovetail plate） | 3.5 kg |
| Rear Thread Type | M42/M48/M54 adapters |
| Rear Connection Distance | Supports 37-68mm range (recommended connection length is 55mm) |
| Standard Package Items | SQA70 OTA in an Oxford cloth case |
| Warranty | 2 Years |
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