• The Askar SQA70 is based on the Petzval optical design, which incorporates two doublet lenses at the front and rear.

• The SQA70 incorporates two pieces of ED (Extra-low Dispersion) glass.

• Light falloff at the edges (vignetting) can degrade image quality by causing uneven brightness and loss of detail.

• The SQA70 design ensures 90% of light is maintained across a 44mm image circle, minimizing vignetting and ensuring more consistent, uniform illumination across the entire image.

• Minimal variation in the focal point of different wavelengths due to the inclusion of ED glass in the SQA70.

• SQA70 results in vibrant, true-to-life colors and sharp, clear images, even in high-contrast or challenging lighting conditions.

• The SQA70 demonstrates exceptional imaging quality, with a central star point RMS radius of less than 1.84 microns, indicating fine resolution at the center.

• The star point at the corners of the image circle is also less than 2.4 microns, showing that sharpness is maintained even at the edges.

• 2.5" Dual speed rack and pinion focuser design.

The Askar SQA70 70mm f/4.8 Super Quintuplet Petzval Astrograph is tailored for both astrophotographers and visual observers. The nature of Quintuplet Petzval designs has a number of unique advantages not seen in other optical designs.

The Askar SQA70 is blueprinted off the Petzval optical design, which normally consists of two doublet lenses in the front and rear which solve for field curvature issues, bypassing the need for a flattener as is typically needed in other optical designs. A secondary benefit of the Petzval is the lack of need to calculate backfocus since the focal plane is already flat, thus as long as the telescope itself is in focus at the center field of view, so will the edges. The SQA70 consists of two pieces of ED glass.

Relative illumination refers to the overall reduction in light intensity and the gradual decrease in brightness that occurs towards the edges of the lens. This phenomenon results from both the natural attenuation of light and optical design limitations. The relative illumination (RI) curve effectively visualizes how the illuminance—measured as a percentage of the center brightness—varies across the imaging sensor. The curve illustrates the change in light intensity from the center of the frame to its outermost edges.

In terms of the graph, the vertical axis represents varying illumination intensities, expressed as different percentages of the example light levels, while the horizontal axis indicates the distance from the center of the image to the edge. Variations in illumination, particularly those causing light falloff at the periphery (also known as vignetting), can negatively impact the image quality, leading to uneven brightness and a loss of detail in the corners.

To minimize this issue, the SQA70 lens is designed to maintain a high level of illumination, ensuring 90% of the light across a 44mm image circle. This advanced design effectively reduces vignetting, providing more consistent and uniform lighting across the entire image.

The longitudinal chromatic aberration curve illustrates the extent to which different light wavelengths, corresponding to various colors, fail to meet at the same focal point. This type of aberration occurs when the various colors of light focus at different distances from the sensor, resulting in color fringing and a loss of sharpness. In the case of the SQA70, the graph shows only extremely minimal variation in where these colors converge, which is a direct result of the inclusion of Extra-low Dispersion (ED) elements in the lens design. These ED elements are specifically engineered to reduce chromatic aberration, ensuring that the light of different colors converges more accurately at the same point. As a result, the lens produces images with colors that remain vibrant and accurate maintaining sharpness and clarity even in challenging lighting conditions and high-contrast exposures.

The imaging performance of an optical system can be assessed by examining the spot diagram, which displays how light rays converge onto the sensor and the resulting distribution of the spots. This analysis helps determine the sharpness and clarity of the image produced by the lens. The SQA70 lens demonstrates exceptional optical quality, with the central star point (the point of maximum focus) having a Root Mean Square (RMS) radius of less than 1.84 microns. This indicates extremely fine resolution at the center of the image. Additionally, the star point at the corners of the image circle is measured to be less than 2.4 microns, which also shows that the lens maintains high sharpness and minimizes distortion even at the edges of the frame. These values suggest the lens performs exceptionally well in terms of maintaining image clarity across the entire field of view, contributing to its overall imaging quality.