Refractor telescope Skywatcher BK 909 EQ2 — 90 mm aperture, 900 mm focal length

The Telescope Skywatcher BK 909 EQ2 90mm aperture 900mm focal length is a compact refractor instrument designed for visual astronomical observation and basic astrophotography on a stable equatorial mount. With a 90 mm objective and 900 mm focal length, it provides a moderate focal ratio suitable for observing the Moon, planets and brighter deep-sky objects. The EQ2 mounting offers manual equatorial tracking and slow-motion controls for targeted adjustments during viewing sessions.

Advantages

This Skywatcher refractor combines a 90 mm objective with a 900 mm focal length to deliver clear, contrasted images at medium to high magnification for solar system targets and brighter nebulae or star clusters. The optical tube’s specification and the equatorial EQ2 mount allow straightforward polar alignment and smoother follow-up of celestial objects. The instrument’s size and mounting make it portable enough for field observation while providing stability for extended visual use.

Suitable for

• Visual observation of the Moon and planets
• Viewing bright deep-sky objects such as open clusters and nebulae
• Beginner astrophotography with short-exposure planetary imaging
• Astronomy education and hobbyist observing sessions

Key specifications

• Optical design: refractor (achromatic doublet)
• Objective aperture: 90 mm
• Focal length: 900 mm
• Focal ratio: f/10
• Mount type: manual equatorial mount (EQ2) with slow-motion controls
• Typical uses: visual observing and short-exposure imaging

How to use

Set the telescope on a level surface and assemble the optical tube on the EQ2 equatorial mount according to the manufacturer’s assembly instructions. Perform a rough polar alignment of the mount using the mount’s polar axis to align with the North Celestial Pole; use the slow-motion controls to track objects as the Earth rotates. Start with a low-power eyepiece to locate the target, then switch to higher magnification eyepieces for detailed observation. For basic planetary imaging, attach a suitable camera to the eyepiece or use a planetary adapter and capture short videos or frames while the mount is tracking manually.

Usage recommendations

Use the telescope away from strong ground lighting for best contrast; allow the optics to reach outdoor temperature for optimal image quality. For more accurate tracking during imaging, consider polar-aligning carefully and using short exposure times to minimize field rotation on a manual equatorial mount.