SVBONY SV193 2″ 0.8x Reducer/Flattener for SV503 102ED

Product Overview

The SVBONY SV193 is a 2″, 0.8x reducer and field flattener made for the SV503 102ED f/7 refractor. It shortens the focal length by 20%, widening the field and speeding up the focal ratio, while flattening the field curvature that is normal for refractors so stars stay round towards the edge of the frame. The optics are 3 elements in 2 groups, fully multi-coated with blackened lens edges, in a hard-anodised aluminium body with a standard M48×0.75 thread and 55 mm backfocus. It weighs 177 g.

Who It's For

This is a good match if you image deep-sky targets with an SV503 102ED and want a wider, faster field than the native f/7 with flat stars across a DSLR, mirrorless or astronomy camera sensor.

Key Features & Design

• 0.8x reduction: shorter focal length and a faster focal ratio for shorter exposures at the same signal.
• Field flattening for round stars toward the corners.
• 3-element / 2-group FMC optics with blackened edges.
• 2″ barrel and M48×0.75 thread.
• 55 mm backfocus from the M48 thread to the sensor.
• Hard-anodised aluminium body.

Optical Design

The three-element corrector sits in the converging light cone ahead of the focal plane. It reduces focal length by 0.8x and corrects the curved focal surface of the objective. Correction depends on placing the sensor 55 mm behind the M48 thread, which is the figure to build your spacing around. SVBONY states that it can also thread onto other f/6–f/7 refractors with 2″ focusers, with limited performance on those.

Recommended Uses

• Deep-sky imaging of larger nebulae, galaxies and clusters with the SV503 102ED.
• Faster sessions: the reduced focal ratio improves signal-to-noise at a given exposure time.

Compatibility and Accessory Notes

• Designed for: SVBONY SV503 102ED f/7. SVBONY makes a separate SV193 version (W9152B) for the SV503 80ED f/7.
• Camera side: M48×0.75; a filter wheel, off-axis guider or astronomy camera can follow it, as long as the total spacing reaches 55 mm.
• Rotation: SVBONY offers a 360° field rotator, sold separately, for changing framing without turning the lens.

If you would like help working out spacers for your camera, filter wheel or OAG, send us your train and we will add it up with you.

Good to Know Before You Order

• Spacing: the sensor needs to sit 55 mm behind the M48 thread; the corners are where the spacing shows.
• Matched to the SV503 102ED: other refractors fit mechanically, with the limited performance SVBONY notes.
• Image circle: SVBONY does not publish an image-circle figure for the SV193.
• Imaging only: it has no application in a visual train.

Frequently Asked Questions

Is it difficult to set up?

It slides into the 2″ focuser like an eyepiece, and the camera threads on the M48 side. The one figure to set is 55 mm from the M48 thread to the sensor, made up with the T-ring or camera spacers.

Does it fit the SV503 80ED?

SVBONY makes a separate SV193 version for the 80ED; this listing is the 102ED version.

Can I use 2″ filters?

Filters go in the camera-side train, for example in a filter drawer or wheel within the 55 mm spacing.

Bottom Line

In short: a 2″ 0.8x reducer/flattener for the SV503 102ED, with 3-element FMC optics and an M48 output at 55 mm backfocus, for a wider, faster and flatter deep-sky field.