GSO DO-GSO 6" F/4 M-LRN OTA Optical tube (GS550)

GSO DO-GSO 6" F/4 M-LRN OTA Optical Tube (GS880)

The GSO DO-GSO 6" F/4 M-LRN OTA is a complete Newtonian optical tube designed for astrophotography, deep-sky observation, as well as viewing the Moon and planets. It combines strong optical performance with a compact and manageable size, making it a versatile choice for both beginners and advanced users.

Optical Tube Construction
The telescope features a classic Newtonian design. The tube is made from rigid rolled steel, ensuring durability and structural stability. The interior is well-blackened to reduce internal reflections, resulting in improved contrast—especially noticeable when observing bright objects such as the Moon and planets.

Optical System
The primary mirror is parabolic and made from high-quality BK7 glass. It has a diameter of 150 mm and a focal length of 600 mm, giving it a fast focal ratio of f/4. The mirror is securely mounted in a solid three-point support cell. The secondary mirror is mounted on a thin yet durable spider, minimizing image distortion and light diffraction. Enhanced aluminum coatings provide approximately 93% reflectivity, ensuring bright and clear images.

Mount Compatibility
The optical tube is designed to work with both alt-azimuth and equatorial mounts with a minimum load capacity of 6 kg.

Focuser System
One of the standout features of GSO telescopes is the high-quality Crayford focuser, manufactured from precision CNC-machined aluminum. This model uses a DO GSO Crayford M-LRN 2" focuser, an improved version of the classic design. The focuser is slightly recessed, allowing the focal point to sit higher above the tube. This design eliminates focusing issues during astrophotography while maintaining proper focus for visual observation.

A distinctive feature is the use of a flat steel guide rail instead of traditional gear mechanisms. This ensures smooth operation without play in any direction and provides excellent resistance to slipping, even under heavy loads. The focuser can handle accessories weighing up to 4 kg.

It also includes a dual-speed microfocus system with a 10:1 ratio, allowing extremely precise focusing adjustments. Two large adjustment screws are present: one for locking the focuser in place (useful with heavy المعدات or to prevent accidental movement), and another for adjusting resistance smoothly. The included adapter allows compatibility with both 1.25" and 2" eyepieces.

Included Accessories

• Tube rings

• Dovetail mounting rail (Vixen standard)

• 8×50 finder scope

• 2" Crayford focuser with 1.25" adapter and microfocus

Technical Specifications

• Optical design: Newtonian

• Aperture: 150 mm

• Focal length: 600 mm

• Focal ratio: f/4.0

• Limiting magnitude: 13.5

• Maximum useful magnification: 300×

• Resolution (Rayleigh): 0.95 arcseconds

• Resolution (Dawes): 0.77 arcseconds

• Light gathering power: 459×

• Tube weight: 4.1 kg

• Tube length: 570 mm

• Tube diameter: 176 mm

• Focuser type: Crayford

• Focuser size: 2"

• Microfocus adjustment: Yes (10:1 ratio)

• Secondary mirror diameter: 50 mm

• Central obstruction: 41%

• Mirror coatings: Aluminum with SiO₂ protective layer

• Mounting rail: Vixen standard

Warranty
The telescope comes with a 24-month warranty provided by the manufacturer.