SVBONY 1.25″ 0.5x Focal Reducer

Product Overview

The SVBONY F9154A is a 0.5x focal reducer in a 1.25″ filter-style cell. It threads onto the M28.5 x 0.6 filter thread of an eyepiece or a 1.25″ camera nosepiece and roughly halves the effective focal length, giving a wider field at lower magnification. The two-element optic is fully multi-coated, the sleeve is all-metal aluminium alloy, and the cell is 20 mm tall with a female M28.5 thread at the rear so a filter can be added.

Who It's For

This is a good match if your telescope's long focal length makes it hard to fit large targets such as the full Moon in the field, or if you image with a small-sensor planetary or EAA camera and want a wider field and shorter exposures.

Key Features & Design

• 0.5x reduction: cuts the telescope's focal length by about half for a wider view.
• Two-element optics: fully multi-coated on all air-glass surfaces for contrast, including on long exposures.
• Threads both ends: male M28.5 x 0.6 at the front, female at the rear for a 1.25″ filter.
• All-metal body: aluminium alloy sleeve, 20 mm total height.

Optical Design

The reducer works by converging the light cone sooner, so the eyepiece or sensor sees a shorter effective focal length. With a filter-thread reducer the actual reduction depends on the distance between the reducer and the focal plane: the further it sits from the sensor or eyepiece field stop, the stronger the reduction. SVBONY rates it at 0.5x.

Recommended Uses

• Lunar observing: fitting the whole Moon in the field on long-focal-length scopes.
• Small-sensor imaging and EAA: a wider field and shorter exposures with planetary-style cameras.
• Low-power visual views: larger open clusters and extended objects.

Compatibility and Accessory Notes

• Thread: M28.5 x 0.6, the standard 1.25″ filter thread on eyepieces and camera nosepieces.
• Filters: a 1.25″ filter threads into the rear.
• C-mount option: SVBONY also offers this reducer with a C-mount adapter as a separate style; get in touch if you need that version.

Good to Know Before You Order

• Small fields: a filter-thread reducer suits small sensors and narrow-field eyepieces best; on larger sensors the edges of the field show vignetting and off-axis aberrations.
• Weight: SVBONY does not publish a weight for this reducer.

Frequently Asked Questions

Is it difficult to set up?

No. It threads onto an eyepiece or camera nosepiece like a filter.

Is it for visual or imaging?

Both. SVBONY presents it for wider-field visual use and for CCD/CMOS imaging.

Can I still use a filter?

Yes. The rear female M28.5 thread accepts a 1.25″ filter.

Bottom Line

In short: a 1.25″, two-element, fully multi-coated 0.5x reducer in a 20 mm metal cell that threads on like a filter to widen the field for observing and small-sensor imaging.