Refractor telescope Skywatcher BK 804 AZ3 80mm aperture 400mm focal length

The Skywatcher BK 804 AZ3 is a refractor telescope with an 80 mm aperture and a 400 mm focal length, supplied with an AZ3 alt-azimuth mount. The instrument is configured for wide-field viewing and delivers bright, high-contrast images suitable for lunar and planetary observation as well as bright deep-sky objects. Its compact optical tube and simple alt-azimuth mount make the setup straightforward for backyard use, outreach events and travel when a portable, easy-to-operate telescope is required.

Advantages

The 80 mm objective gathers enough light for clear views of the Moon, planets and larger star clusters while keeping the instrument lightweight. The short 400 mm focal length produces a wide apparent field of view, facilitating low- to medium-power observations and making star-hopping and framing of extended objects easier. The included AZ3 mount provides intuitive altitude-azimuth movement for quick target acquisition and tracking by hand, and the overall package is compact for storage and transport.

Suitable for

• Visual lunar and planetary observation
• Wide-field views of open clusters and bright nebulae
• Beginner astronomy and outreach demonstrations
• Portable observing sessions and travel

Key specifications

• Optical type: refractor (achromatic design)
• Aperture: 80 mm
• Focal length: 400 mm (f/5)
• Mount type: alt-azimuth (AZ3)
• Typical use: visual observation of solar system and bright deep-sky objects
• Form factor: compact and lightweight optical tube

How to use

Assemble the optical tube on the AZ3 mount following the supplied instructions, ensuring the dovetail or mounting bracket is securely fastened. Start with a low-power eyepiece to locate targets and centre them in the field, then switch to higher magnification as needed. Use the mount’s altitude and azimuth controls to point and track objects manually; the short focal length gives a wide field that eases locating targets. Balance the setup on the mount and tighten adjustment knobs to maintain stability during observation.

Recommendations

For best observing results, allow the telescope to reach thermal equilibrium with the outside temperature before making high-magnification observations. Use low- to medium-power eyepieces for wide-field viewing and switch to higher powers only when atmospheric seeing is steady. Store the telescope in a dry place and protect the objective lens with a cover when not in use to preserve optical performance.