Aurel Clarion UHC filter 31 mm, premium grade

Specifications

Description

The Clarion UHC filter is an unmounted 31 mm round nebula filter for filter wheels and filter drawers. Its 28 nm passband covers the hydrogen-beta and doubly ionized oxygen lines, and a second passband transmits the hydrogen-alpha line in the red.

Used with a color camera, the Clarion UHC records emission nebulae with high contrast against a darkened sky. The combination of a blue-green and a red passband keeps a natural-looking balance between hydrogen and oxygen regions, so nebulae such as the Lagoon, the Trifid, and the Orion Nebula show their familiar colors.

Under light pollution and moonlight, the filter makes it possible to image emission nebulae on nights that would otherwise be too bright. It works with one-shot color cameras and, in a filter wheel, alongside other filters for monochrome cameras.

The filter is less suited to galaxies and star clusters, which shine across the spectrum. For those targets, use a broadband filter or no filter. Stars recorded through the Clarion UHC appear with a slight color shift, which processing can correct.

The 31 mm size fits filter wheels designed for unmounted 31 mm filters and covers smaller camera sensors. Check your sensor size and filter wheel spacing before you choose.

The glass has a multi-layer interference coating on one side and an anti-reflection coating on the other, which keeps halos around bright stars small in stacked images.

The Clarion UHC suits imagers with small sensors who want to capture emission nebulae from suburban sites with a single filter.

About this configuration

The Aurel Clarion UHC filter 31 mm is offered in several configurations, and the notes below describe what this particular one includes. The premium grade uses polished glass with tighter flatness tolerances, which helps at high magnification. Premium grade filters are checked for the position of the passband before they leave the factory. Anti-reflection coatings on both faces reduce halos around bright stars in the field.

The aluminum case protects the filter from crushing in a crowded accessory box. This is the 2024 edition, which revised the cell knurling and the case insert of the Clarion line. A filter does not make objects brighter; it darkens the sky background more than the target, which raises contrast.

What's in the box

• UHC filter, unmounted 31 mm round
• Plastic storage case
• Aluminum storage case

Compatibility notes

• Fits filter wheels and holders that accept 31 mm unmounted filters.
• Covers sensors up to about 4/3 in size in typical filter wheel spacing.
• Pairs with one-shot color cameras and with monochrome cameras in a filter wheel.