SVBONY 1.25″ UHC Light Pollution Filter

Product Overview

The SVBONY F9131A is a 1.25″ UHC (Ultra High Contrast) filter in a standard M28.5 x 0.6 cell. It is a narrower-passband light pollution filter than a CLS: it reduces light from mercury-vapour and sodium-vapour lamps and the natural oxygen airglow of the atmosphere, while passing the emission lines of nebulae. The result is a darker sky background and higher contrast on emission and planetary nebulae. The coated optical glass is 1.85 mm thick in an aluminium frame, and the filter ships in a transparent storage case.

Who It's For

This is a good match if you observe or image emission nebulae from urban or suburban skies through a 1.25″ eyepiece or imaging train and want the background darkened noticeably more than a broadband filter would.

Key Features & Design

• Ultra-high contrast passband: selectively reduces artificial-light wavelengths so emission nebulae stand out from the sky.
• Darker background: SVBONY rates the sky background darker and nebula contrast higher than with typical broadband filters.
• Optical glass in an aluminium frame: 1.85 mm coated substrate built for frequent use.
• Standard 1.25″ cell: M28.5 x 0.6 thread fits most 1.25″ eyepieces, diagonals and accessories.
• Storage: supplied in a transparent case.

Recommended Uses

• Visual observing of emission nebulae: the Orion, Lagoon, Swan and Veil nebulae from suburban sites.
• Planetary nebulae: the Ring and Dumbbell show more clearly against a darkened background.
• Colour imaging under bright skies: more contrast on emission targets with a 1.25″ imaging train.

Compatibility and Accessory Notes

• Thread: M28.5 x 0.6, the standard 1.25″ filter thread on eyepieces, diagonals and nosepieces.
• Other sizes: SVBONY also makes this filter in 2″ (F9131B, M48 x 0.75) and as a Canon EOS-C clip-in (F9131D).
• UHC vs CLS: the UHC has the narrower passband and suits brighter skies; SVBONY's CLS filter is the wider option for less light-polluted sites.

What's in the Box

• 1 x 1.25″ UHC filter (F9131A)
• 1 x transparent storage case

Good to Know Before You Order

• Best on emission objects: galaxies and star clusters are broadband targets and gain little from a UHC filter.
• Dimmer stars and colour shift: the narrower passband dims stars visually and gives images a colour cast that is corrected in processing.
• Weight: SVBONY does not publish a weight for this filter.

Frequently Asked Questions

Is it difficult to set up?

No. It threads into the filter thread at the bottom of a 1.25″ eyepiece or the nosepiece of a diagonal.

Is it for visual use or imaging?

Both. SVBONY presents it for visual observing and astrophotography.

Should I choose UHC or CLS?

Under brighter suburban or city skies the UHC gives more contrast. Under moderately dark skies the wider CLS keeps more starlight. Get in touch if you want help choosing.

Bottom Line

In short: a 1.25″ M28.5 UHC filter that darkens light-polluted skies and lifts emission and planetary nebulae, for visual observing and imaging through standard 1.25″ gear.