SVBONY SV209 1.0x Field Flattener for SV550 80 f/6

Product Overview

The SVBONY SV209 is a 1.0x field flattener for the SVBONY SV550 80 f/6 refractor. It corrects the field curvature of the SV550 80 so stars stay sharp toward the edge, without changing focal length, and delivers a 45 mm fully illuminated field that supports full-frame sensors. It is a two-lens, fully multi-coated design in a 67 mm housing, 87.5 mm long without the male thread, and comes as three parts: the flattener, an M63 extension tube and an M48 adapter ring with a built-in 2″ filter thread.

Who It's For

This is a good match if you image with an SV550 80 f/6 and want a flat field across an APS-C or full-frame sensor at the telescope's native focal length.

Key Features & Design

• 1.0x factor: no change in focal length at the focal plane.
• 45 mm fully illuminated field for full-frame sensors.
• Two-lens FMC optics.
• M63×1 telescope connection after removing the SV550's 2″ adapter ring.
• M48 adapter ring with 2″ filter thread, so any 2″ filter can sit in the train.
• Connection for the SV210 camera angle adjuster (sold separately).

Optical Design

The two-element flattener sits in the converging cone of the SV550 80's objective and reshapes its curved focal surface into a flat one, keeping the 1.0x focal length. The M63 extension tube and the M48 adapter ring together set the flattener's back focal length to 55 mm at the M48 male thread; the camera side also offers an M63×1 female thread with a 103 mm working distance for other photo adaptations. SVBONY also lists a 91.5 mm working distance at the M48 thread.

Recommended Uses

• Deep-sky imaging with the SV550 80 f/6 on full-frame and APS-C cameras.
• Wide-field nebula and Milky Way fields at the native 1.0x focal length.
• Filter imaging with a 2″ filter in the M48 adapter ring.

Compatibility and Accessory Notes

• Telescope: SVBONY SV550 80 f/6 (80 mm APO).
• Assembly: unscrew the SV550's 2″ adapter ring, then connect the flattener, the M63 extension tube and the M48 adapter ring in the order SVBONY shows; the order matters for the 55 mm figure.
• Camera: SVBONY's example uses a Canon-compatible camera at 55 mm; any camera can be spaced to 55 mm from the M48 thread.
• SV210 CAA: the SV209 connects to the SV210 camera angle adjuster for rotating the framing.

If you would like the train worked out for your camera, filter and rotator, send us your parts list and we will add it up with you.

What's in the Box

• SV550 80 OTA field flattener
• M63 extension tube
• M48 adapter ring

Good to Know Before You Order

• Matched to the SV550 80 f/6: the SV209 0.8x reducer for the SV550 122 is a different product.
• Spacing: 55 mm from the M48 thread to the sensor; the corners are where the spacing shows.
• Mount not included; SVBONY does not publish a weight for this flattener.
• Imaging only: it has no application in a visual train.

Frequently Asked Questions

Is it difficult to set up?

It takes a few minutes: remove the SV550's 2″ adapter ring, thread on the three parts in order, and space the camera to 55 mm from the M48 thread with the T-ring or spacers.

Does it reduce focal length?

No. It is a 1.0x flattener.

Will it cover full frame?

SVBONY publishes a 45 mm fully illuminated field supporting full-frame sensors.

Can I use 2″ filters?

Yes. The M48 adapter ring has a built-in 2″ filter thread.

Bottom Line

In short: a two-lens 1.0x field flattener for the SV550 80 f/6, with a 45 mm illuminated field, 55 mm backfocus at its M48 output and a 2″ filter thread, for flat full-frame deep-sky images.