The SVBONY SV209 0.8× Focal Reducer / Field Flattener is specifically designed for the SV550 122mm f/7 Triplet APO refractor. It optimises the telescope for wide-field astrophotography by reducing focal length and correcting field curvature, resulting in faster imaging and sharp stars across the entire sensor.

Key Features

• 0.8× Focal Reduction
  Reduces the effective focal length by 20%, delivering a wider field of view and shorter exposure times.
• Field Curvature Correction
  Flattens the naturally curved focal plane of refractor telescopes, improving edge-to-edge star sharpness.
• Brighter, Faster Imaging
  Converts the SV550 122mm from f/7 to approximately f/5.6, increasing imaging speed for deep-sky targets.
• Designed for SV550 122 Triplet APO
  Precisely matched to the optical characteristics of the SV550 122mm triplet refractor for optimal performance.
• Fully Multi-Coated Optics
  High-quality coatings reduce reflections and aberrations, maintaining contrast and image clarity.

0.8× Reducer / Field Flattener for SV550 122mm APO

By shortening the focal length from 854 mm to approximately 683 mm, the SV209 enables wider framing of large nebulae and improved efficiency when imaging faint deep-sky objects.

Installation Overview

1. Remove the existing focuser adapter from the SV550 122mm telescope
2. Thread the SV209 reducer/flattener directly into the focuser
3. Attach camera adapters and imaging accessories as required

Mechanical Structure & Threading

The reducer/flattener threads directly into the focuser for a rigid, tilt-resistant connection. The main telescope-side thread is M63×1, providing secure mechanical alignment.

Correction of Field Curvature

In addition to focal reduction, the SV209 corrects the inherent field curvature found in refractor telescopes. This ensures stars remain sharply focused to the edges of DSLR and astronomy camera sensors.

Backfocus Specification – 55 mm

The required backfocus distance is 55 mm, measured from the shoulder of the reducer to the camera sensor. This spacing matches the standard requirement for DSLR and many dedicated astronomy cameras.

Fully Multi-Coated Optical System

The fully multi-coated lens elements improve light transmission and reduce internal reflections. The SV209 transforms the SV550 122mm f/7 refractor into a faster f/5.6 imaging system, making it well suited for both astronomical and terrestrial photography.

Compatibility Notes

• Designed specifically for the SV550 122mm f/7 Triplet APO refractor
• Optimised for 55 mm backfocus spacing
• Best results achieved with rigid, well-aligned imaging trains
• Not guaranteed to perform optimally on other telescope models