SharpStar SCA260 V2 260mm f/5 Super Cassegrain Astrograph

260mm Aspherical Primary and 3-Element Corrector System

At the heart of the SCA260 V2 is a 260mm aspherical primary mirror, a design that demands a far more sophisticated manufacturing and testing process than a simple spherical mirror. This advanced optical surface provides superior correction across the field. The primary is made from PZ33, a Pyrex-like glass that is more stable than the mirror materials traditionally used, which helps the optics stay consistent as temperatures change overnight.

• Enhanced Aluminum Coatings: Both the primary mirror and the 120mm spherical secondary mirror feature high-reflectivity coatings that deliver more than 95% reflectivity, resulting in brighter images and shorter exposure times.
• Three-Element Corrector: A 3-inch, three-element air-spaced corrector sits in the optical path. SharpStar uses it so the whole system can better achieve full-frame imaging and keep vignetting under control.
• Aspherical Advantage: By correcting optical aberrations at the primary mirror itself, the design achieves a higher level of sharpness and contrast, which is critical for resolving fine details across the enormous imaging field.

A Massive 80mm Corrected Image Circle

The SCA260 V2 has an 80mm image circle. The 3-inch three-element corrector is there so the f/5 system can better achieve full-frame imaging and control vignetting, which makes the astrograph a strong match for large-sensor CMOS and CCD cameras.

This enormous field of view allows you to capture vast nebulae complexes and galaxy clusters in a single frame, or create ultra-high-resolution mosaics with fewer panels. A full-frame sensor (43mm diagonal) and a medium-format chip such as the IMX461 (55mm diagonal) both fit well inside the 80mm circle.

The Imaging Advantages of a 1300mm f/5 System

The combination of a 260mm aperture and a 1300mm focal length strikes a powerful balance between image scale and light-gathering power. The f/5 focal ratio is much faster than slower f/8 or f/10 systems, allowing you to collect data on faint deep-sky objects much more quickly. This speed reduces individual sub-exposure times, minimizing the impact of tracking errors and changing atmospheric conditions.

With a theoretical resolution of 0.46 arc-seconds, the SCA260 V2 has the resolving power to capture intricate details in spiral arms of galaxies like the Whirlpool Galaxy (M51) and resolve individual stars in dense clusters like the Hercules Cluster (M13). The 1300mm focal length provides the ideal image scale for many popular deep-sky targets when paired with modern CMOS sensors.

14.5kg Carbon Fiber Tube and Thermal Stability

The optical tube is constructed from a lightweight yet rigid carbon fiber material. This offers two key advantages for astrophotography: a high stiffness-to-weight ratio and minimal thermal expansion. The total OTA weight of 14.5kg places it within the payload capacity of many popular mid-to-high-end equatorial mounts.

Carbon fiber's near-zero coefficient of thermal expansion means that the distance between the primary and secondary mirrors remains constant as the temperature drops. This keeps the focal point stable throughout a long imaging session, preventing focus drift that can ruin hours of data. As with any large reflector, give the telescope time outdoors to reach ambient temperature before imaging.

3.35" Focuser, 360° Rotator, and 70mm Back Focus

The SCA260 V2 is equipped with a dedicated 3.35" focuser whose load capacity SharpStar has upgraded, so it carries imaging accessories with no slippage and smooth operation. SharpStar also extended its travel to 50mm for greater practicability. The rear of the focuser incorporates several features essential for a modern imaging setup.

• 360° Rotator: A 360° rotator at the rear of the focuser lets you frame your target without loosening the camera, which helps when composing mosaics or finding a guide star. SharpStar placed it behind the focusing unit so an EAF cable does not get tangled as you rotate.
• 70mm Back Focus: A generous 70mm of back focus is available from the M48x0.75 thread, providing ample room for accessories like filter wheels, and off-axis guiders.
• Versatile Connections: The focuser includes a system of adapter rings for M68x1, M54x0.75, and M48x0.75 threads, making it easy to connect to most imaging cameras and accessories on the market. A built-in 2-inch filter thread is also included for added flexibility.

Mounting Points and Simplified Optical Alignment

The SCA260 V2 is designed for practical field use. It includes a CNC-machined handle bar that not only makes transport easier but also serves as a mounting platform for guide scopes or other accessories.

SharpStar has also simplified the optical axis mechanics: to adjust the secondary mirror, you only need to work its pull rod. Like any reflecting telescope, the SCA260 V2 benefits from a collimation check from time to time, and keeping it aligned is how you get the most out of its 0.46 arc-second resolution.