The SVBONY SV209 1.0× Field Flattener is designed specifically for the SV550 80mm f/6 refractor, correcting field curvature without altering focal length. It delivers sharp, flat images across the entire sensor, making it ideal for wide-field astrophotography with modern cameras.

Key Features

• 1.0× Field Flattening (No Focal Reduction)
  Maintains the native focal length of the telescope while correcting field curvature for edge-to-edge star sharpness.
• Optimised for Wide-Field Imaging
  Ensures consistent focus and clarity across the frame, particularly beneficial for APS-C and full-frame sensors.
• Fully Multi-Coated Optics
  High-quality coatings maximise light transmission and reduce aberrations, preserving contrast and image detail.
• Designed for SV550 80mm f/6 OTA
  Precisely matched to the optical design of the SV550 80F6 for correct spacing and optimal performance.
• Robust Mechanical Construction
  Precision-machined metal housing ensures stable alignment during long imaging sessions.

Field Curvature Correction for SV550 80F6

Most refractor telescopes exhibit some degree of field curvature. The SV209 corrects this curvature, ensuring stars remain pinpoint sharp from the centre of the image to the edges, greatly improving astrophotography results.

Backfocus Specification – 55 mm

Correct backfocus spacing is essential for optimal performance. The SV209 is designed around a standard 55 mm backfocus, measured from the shoulder of the flattener to the camera sensor.

This spacing is ideal for DSLR and many dedicated astronomy cameras when used with the supplied adapters.

Mechanical Structure & Threading

The SV209 threads directly into the telescope focuser for a rigid, tilt-resistant connection. The telescope-side thread specification is:

• M63×1 male thread

M63 Extension Tube Included

The supplied M63 extension tube and M48 adapter ring ensure the correct 55 mm backfocus spacing, following standard astrophotography conventions.

M48 Adapter Ring & 2-Inch Filter Support

The M48 adapter ring includes internal 2-inch filter threads, allowing direct installation of standard 2-inch filters. This enables flexible use of light-pollution, narrowband, or UV/IR-cut filters within the imaging train.

Expandable Imaging Configuration

The SV209 can also be combined with the SV210 camera angle adjuster (sold separately) to fine-tune image framing and field orientation without disturbing focus or spacing.

Compatibility Notes

• Designed specifically for the SV550 80mm f/6 refractor
• Maintains native focal length (1.0×)
• Optimised for 55 mm backfocus spacing
• Supports 2-inch filter systems via M48 threading
• Not guaranteed to perform optimally on other telescope models