Aurel Clarion H-beta filter 2 in, observatory grade

Specifications

Description

The Clarion H-beta is a hydrogen-beta line filter in a 2 in threaded cell. Its 24 nm passband, centered on 486 nm, is wider than that of most H-beta filters, which lets through more light while still darkening the sky background substantially.

The wider passband makes the Clarion H-beta easier to use in medium telescopes. In a 200 mm Dobsonian under dark skies, it can show the glow of IC 434 behind the Horsehead Nebula and the brighter parts of the California Nebula. In large telescopes, the extra light makes these objects easier to hold with direct vision.

The trade-off is contrast. A wider passband lets through more sky background than a narrow filter, so under bright suburban skies the effect is smaller. The Clarion H-beta works best at rural and dark sites.

Use a low-power eyepiece with the filter, so the exit pupil is large and the view stays bright. Find the target without the filter first, then add it, since the filter dims field stars along with the background.

The 2 in cell threads into eyepieces, diagonals, and filter wheels. It can stay in a 2 in diagonal while you change eyepieces, which is convenient for comparing views at different magnifications.

The glass is float glass with a multi-layer interference coating on one side and an anti-reflection layer on the other. Clean it with a blower and, if needed, lens fluid on a soft tissue.

The Clarion H-beta suits observers who want to try the Horsehead and the California Nebula without the cost of a narrow-band filter made on polished glass.

About this configuration

The Aurel Clarion H-beta filter 2 in is offered in several configurations, and the notes below describe what this particular one includes. The observatory grade comes with a measured transmission curve for the individual filter in the box. Observatory grade glass has the tightest flatness tolerance in the Clarion line, which suits imaging with long focal lengths. 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 2026 edition, the most recent version of the Clarion line in the catalog. A filter does not make objects brighter; it darkens the sky background more than the target, which raises contrast.

What's in the box

• H-beta filter in 2 in threaded cell
• Plastic storage case
• Test report with measured transmission curve
• Aluminum storage case

Compatibility notes

• Threads into 2 in eyepieces, diagonals, and filter wheels (M48 x 0.75).
• Most effective in telescopes of 200 mm aperture and larger under dark skies.