GSO 10" F/8 M-LRC-D Ritchey-Chretien OTA

Description

GSO 10" f/8 Ritchey-Chrétien Astrograph Telescope (M-LRC-D Model)

The GSO 10" f/8 Ritchey-Chrétien Astrograph Telescope represents a new level of precision and optical performance for serious astrophotographers and observatories. Built with the legendary Ritchey-Chrétien (RC) optical design and enhanced by 3" M-LRC dual-speed linear bearing focuser, this optical tube assembly (OTA) delivers the clarity, stability, and reliability demanded by professionals and advanced amateurs alike.

A True Ritchey-Chrétien Optical Design

Unlike classical Cassegrain or Schmidt-Cassegrain systems, which use spherical or parabolic mirrors, the Ritchey-Chrétien employs hyperbolic primary and secondary mirrors. This design eliminates both coma and spherical aberration, resulting in sharp, coma-free star images across a large, flat field. That’s why all major professional observatories and space telescopes — including the Hubble Space Telescope — use the RC design.

The GSO 10" RC brings this professional-level optical precision to the amateur astronomer at a fraction of the cost. With its 254 mm aperture and 2000 mm focal length (f/8), it provides both high resolution and sufficient image scale for deep-sky imaging, while maintaining a manageable size for field or observatory use.

Fused Quartz Optics – Thermal Stability and Accuracy

Both the primary and secondary mirrors are made from fused quartz, a material prized for its extremely low coefficient of thermal expansion. Unlike standard Pyrex or BK7 glass, fused quartz maintains its shape even under temperature variations, ensuring consistent focus and image sharpness throughout long imaging sessions.

Each mirror features high-precision optical figuring to 1/12 λ RMS and is coated with 99% dielectric coatings, providing maximum light reflectivity and long-term protection from oxidation or tarnish. The result is high-contrast, high-brightness images with minimal light loss — perfect for faint galaxies, nebulae, and other deep-sky targets.

Durable Steel Optical Tube

The optical tube of the GSO 10" Ritchey-Chrétien is made of high-quality steel, offering exceptional mechanical strength and long-term stability. Steel construction ensures precise optical alignment and minimizes flexure, even when the telescope is equipped with heavy imaging gear.

Unlike lighter composite materials, the steel tube provides solid thermal inertia, allowing gradual temperature equalization and reducing sudden focus shifts. Its interior is coated with a flat black, anti-reflective finish and features a new multiple knife-edge baffle system to effectively suppress stray light and maximize image contrast.

While slightly heavier than carbon fiber, the steel tube offers superior rigidity, excellent vibration resistance, and a durable, professional appearance — ideal for both observatory and field use.

Precision 3" M-LRC Dual-Speed Crayford Focuser

The GSO 10" f/8 RC OTA is equipped with GSO’s premium 3-inch M-LRC focuser. This focuser features a linear bearing rail system that supports the drawtube along its entire travel, ensuring smooth, rigid, and backlash-free focusing even under heavy imaging loads.

With dual-speed control (10:1 fine focus), users can make both coarse and ultra-fine focus adjustments easily, essential for critical focusing with high-resolution cameras. The focuser is also EAF-compatible, allowing connection to an Electronic Auto Focuser for precise, automated focusing during astrophotography sessions.

The focuser’s large M69x1 female thread and included 2" and 1.25" adapters make it compatible with a wide range of cameras, diagonals, and accessories. This flexibility allows you to configure the imaging train exactly as needed for your specific setup.

Generous Back Focus and Mounting Flexibility

With a back focus distance of 300 mm from the rear cell, the GSO RC provides ample space for attaching imaging accessories such as filter wheels, off-axis guiders, field flatteners, and CCD/CMOS cameras.

The OTA is fitted with dual Losmandy-style dovetail plates, allowing secure attachment to most equatorial mounts while also providing multiple mounting points for accessories like guide scopes, finder scopes, or dew heaters. The design ensures a solid and balanced setup even with heavy imaging gear.

High Resolution and Contrast

The telescope’s optical design and quality materials combine to deliver a resolution of 0.46 arcseconds, enabling the capture of exceptionally fine details. The large secondary mirror (112 mm obstruction, 85 mm clear diameter) provides a fully illuminated field suitable for large-format sensors, making this telescope ideal for professional imaging applications.

The internal baffle system and precisely blackened optical surfaces further improve image contrast by suppressing stray light and reflections, resulting in clean, high-contrast astrophotos even under less-than-perfect sky conditions.

Built for Advanced Imaging

This telescope is designed primarily as an astrograph — optimized for imaging rather than visual use. It produces a wide, well-corrected field ideal for large-format CCD or CMOS cameras. When paired with a suitable field flattener, the GSO 10" RC can achieve pinpoint stars all the way to the edges of full-frame sensors.

Its f/8 focal ratio offers a great balance between image scale and exposure time, making it versatile for a wide range of deep-sky objects — from small galaxies and planetary nebulae to large emission nebulae and star clusters.

Performance and Value

GSO (Guan Sheng Optical) has earned worldwide recognition for producing precision optical instruments at exceptional value. The 10" f/8 Ritchey-Chrétien OTA is one of the best examples of this philosophy — offering professional-grade optics, mechanical quality, and imaging performance at a price accessible to dedicated amateurs.

This OTA is an excellent choice for those looking to step up from refractors or Schmidt-Cassegrains into true astrographic systems. Whether you are running a personal observatory or imaging remotely, the GSO RC delivers the consistency, precision, and reliability that astrophotography demands.

Specifications – GSO 10" f/8 Ritchey-Chrétien Astrograph (M-LRC-D)

The following pictures were taken with a GSO 10" F/8 M-LRC-D Ritchey-Chrétien Telescope, paired with various astrophotography accessories, Source: GSO 10" f/8 Ritchey-Chretien - AstroBin