Introducing the Askar SQA55 55mm f/4.8 Petzval Astrograph, where precision optics meet cutting-edge design to redefine astrophotography. Engineered for celestial enthusiasts and professionals alike, this revolutionary lens combines the classical Petzval design with modern optical advancements, delivering unparalleled clarity and breathtaking detail in capturing the wonders of the night sky. SQA55 Features Petzval Lens Structure: Self-flattened design, no need to calculate specific back focus between 50mm and 60mm connection distance, users can directly use it for shooting after the OTA is in focus Super Fine Star Point: Quintuplet air-spaced lens design, including 1 piece of SD glass and 1 piece of ED glass. The central star point has an RMS radius of less than 2.5 μm, and the star point at the corner is less than 4 μm, showing a super fine star point. Filter Thread: At the end of the OTA, it is equipped with a M48 adapter, which has a built-in 2" filter thread for direct connection of 2" filters. Quick Release Base Position: There are four multi-functional quick release bases on the rear of the lens tube, which can be used to connect various accessories for photography and astrophotography, and can also be perfectly matched with the accessories of the SQA series. Lens Hood Special Reversible Design: The lens hood is fixed by a slot, when the lens is not in use, it can be stored on the lens barrel in reverse to reduce the overall volume, and when using it, it only needs to be stuck on the lens. Variable-Aperture Lens: The aperture range of the lens is from f/22 to f/4.8, with a graded adjustment ring and a scale labeled on the lens tube to prevent accidental touching and save the adjustment parameters. SQA55 Functionality Camera Quick Release Base: Camera quick-release knobs on the top handle and the bottom bracket, which can be used to convert the OTA to camera lens mode manually and quickly without additional tools. Quick-Release Handle: The handle has a finder base slot, which can connect different astronomical accessories. The handle is a quick-release design and can be removed without additional tools. Bottom Bracket: The bottom bracket has 1/4" and 3/8" screw holes for attaching a tripod Dovetail Plate: The dovetail plate is a standard Vixen-style 200mm dovetail plate. The bottom of the dovetail plate is designed with hand screws and a quick-release knob, which can be disassembled and assembled without additional tools. M67 Filter Thread: The front of the lens is designed with a M67 filter thread which can be connected to camera filters, convenient for daily photography Diversified Photography Scene Applications: Optical and mechanical design optimized for both astronomical photography and daily photography, it can be used to connect to astronomy cameras to take star photos or connect to DSLR or mirrorless cameras to be used as camera lenses. Dual-Speed Focuser Design: Fine adjustment and coarse adjustment can both be adjusted independently. Fine adjustment designs a central indicator point, a focusing travel of ± 1mm, and a locking screw. The coarse adjustment is engraved with a reference scale for focusing distance in both imperial and metric markings. In daily photography, focusing can be adjusted according to the focusing scale for reference. The coarse adjustment can be rotated to the infinity mark for focusing, and there is still a certain amount of leeway after the infinity mark, thanks to the self-flattened design, between 50mm and 60mm connection distance, users can directly using it for shooting after the OTA is in focus, which makes it easy to connect the telescope with the necessary accessories. Coarse adjustment is designed with a locking screw for individual adjusting. Dual Rotator Design: The lens tube and 360° rotator both have independent locking screws. For daily shooting, the whole body can be rotated. For astrophotography, the high-precision rotator can be rotated independently, while the rotator is engraved with a scale, which is convenient for adjusting and saving the angle. Specifications Aperture 55mm Focal Length 264mm Focal Ratio f/4.8 Objective Type Quintuplet Petzval APO（one piece of SD glass & one piece of ED glass） Image Circle 44mm Aperture Blades 14 blades Graded Aperture f/4.8 - f/22 Focusing Type Manual focus Filter Diameter M67 Rear-End Adapter M48*0.75 (with M48×0.75 filter thread) Rear-End Connection Distance Supports 50-60mm range (Recommended connection length is 55mm) Total Length 316mm (inclulding dew shield); 244mm (without dew shield) OTA weight 1840 g Total weight (including handle & dovetail plate) 2180 g Optical Path The SQA55 is a quintuplet air-spaced lens design, including 1 piece of SD glass & 1 piece of ED glass. MTF Chart In the two sets of curves corresponding to low and high frequencies, even at the edge of the full frame the sagittal lines and sagittal lines distance of the SQA55 lens remain very small, and at the low frequency of 10LP/mm, it is higher than 0.9 overall, showing the high resolution and sharpness of the SQA55. Relative Illumination: The SQA55 guarantees a high illumination of about 90% even at the edge of the full frame, minimizing vignettings. Spot Diagram The imaging quality of the optical system can be evaluated by analyzing the distribution of the spots on the spot diagram. The SQA55 has a central star point with an RMS radius of less than 2.5 µm, and the star point at the corner is less than 4 µm, showing fine star point. ZYGO Objective Chart: The ZYGO interferometer is internationally recognized as a more authoritative instrument for testing optical lens quality, and the SQA55 test results show great star quality.
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