GSO DO-GSO Dobson 10" F/5 M-CRF Telescope (GS880)

The Delta Optical GSO Dobson 10" F/5 M-CRF is a large Newtonian telescope designed for both beginners and advanced sky enthusiasts who seek demanding, high-quality visual observing. This telescope delivers bright, sharp, and clear images, making it excellent for visual astronomy. Its size allows it to show all Messier objects and most NGC objects, with the best performance under dark rural skies. In the hands of an experienced observer, the Delta Optical GSO Dobson 10" enables very advanced observations. Despite its substantial size, it remains highly portable and fits easily in a standard car.

Optical Tube
The optical tube follows the classic Newtonian design and is made from rigid rolled steel. The interior is carefully blackened to reduce reflections and enhance contrast, especially when observing bright objects such as the Moon and planets.

Optical System
The parabolic primary mirror is made from high-quality BK7 glass, with a diameter of 250 mm, an f/5 focal ratio, and a focal length of 1250 mm. The mirror is mounted in a robust cell with three support points. The secondary mirror is mounted on a thin, durable spider to minimize diffraction and reflections. Enhanced aluminum coatings provide a reflectivity of about 93%.

Mount
Setup is easy and straightforward. The telescope uses a box-type Dobsonian mount, which does not require alignment with the cardinal directions or the celestial pole. The Dobsonian mount is simple, very stable, and capable of supporting significant weight, allowing easy rotation in both altitude and azimuth axes. The tube is held in a fork mount with metal trunnions, each with a locking knob for secure adjustment. Roller bearings ensure smooth and light movement in azimuth. The low center of gravity and stiff materials make the setup far more stable than equatorial mounts. GSO Dobsonians also feature a tube balance system to adjust for different eyepiece weights.

Focuser
A hallmark of GSO telescopes is the high-quality Crayford focuser, made from precisely machined CNC aluminum. Four bearings and a guide roller enable smooth, precise movement without any play. All Delta Optical GSO telescopes are equipped with dual-speed (10:1) microfocusers for extremely accurate focusing, even with demanding eyepieces. The focuser has two large adjustment knobs: one for locking focus—useful with heavy accessories—and the other for smooth tension control. Both 1.25” and 2” eyepieces are supported. The focuser’s load capacity is about 3 kg.

Cooling
Delta Optical-GSO Dobson telescopes come with a cooling fan located under the primary mirror. Powered by 12V (using the included 8xAA battery holder), the fan improves air circulation around the mirror, accelerating cool-down.

Terrestrial Observing
This type of telescope is not ideal for terrestrial observation, as the image is inverted. To correct this, an erecting lens is required. With the lens and the Dobsonian mount, it can be used for simple terrestrial viewing. The stable and easy-to-use mount makes it a great tool for spotting airplanes at cruising altitudes.

Astronomical Observing

Solar System:

• Lunar surface details under 3 km in size

• All planets of the solar system

• Phases of Mercury and Venus

• Mars’ disk, polar caps at opposition, and surface details

• Jupiter’s cloud bands and Galilean moons

• Saturn’s rings with Cassini Division, cloud bands, and moons

• Uranus and Neptune as small, distinct blue disks

• Tracking asteroids among the stars

• Observing faint comets

Stars:

• Stars across the sky down to about 15.5 magnitude

• Double and multiple star systems

Deep Sky:

• All Messier objects and most NGC objects

The 25 cm mirror diameter makes objects much clearer and details far more apparent than in smaller telescopes. However, such a large telescope is more sensitive to light pollution, air quality, atmospheric stability (seeing), and collimation accuracy. These factors must be considered to achieve optimal results.

Included Accessories

• 1.25" 9 mm eyepiece

• 2" 30 mm eyepiece

• 2" 35 mm extension tube

• 8x50 straight finderscope

• Cooling fan for primary mirror with battery holder

Specifications

Catalog Number: GS880
Optical Design: Newtonian
Mount Type: Dobsonian
Aperture: 254 mm
Focal Length: 1250 mm
Focal Ratio: f/5.0
Limiting Magnitude: 14.6
Maximum Useful Magnification: 508x
Maximum Resolution (Rayleigh): 0.56"
Maximum Resolution (Dawes): 0.46"
Light Gathering Power: 1317x
Tube Weight: 16.1 kg
Mount Weight: 13.6 kg
Total Weight: 31 kg
Tube Length: 1210 mm
Tube Diameter: 305 mm
Tripod Height: 60 cm
Mount Control: Manual
Focuser Type: Crayford
Focuser Diameter: 2"
Focuser Micro-motion: Yes
Secondary Mirror Diameter: 63 mm
Central Obstruction: 25%
Coatings: Aluminum with SiO3 overcoat
Warranty: 24 months