Pellucid Lucent H-beta narrowband filter 1.25 in, observatory grade

Specifications

Description

The Lucent H-beta is a narrowband nebula filter that passes the hydrogen-beta emission line at 486.1 nm in a 1.25 in threaded cell. Its passband is about 8 nm wide at half maximum, so it admits that line while blocking most of the broadband light from the sky and from artificial lighting. Peak transmission is 95 percent at the center of the band. The cell is machined from aluminum and fitted with a threaded rim, so the filter can be mounted without adapters.

Emission nebulae radiate at specific wavelengths, while the sky background spreads its glow across the visible spectrum. A narrow band centered on hydrogen-beta lets through a larger share of the nebula's light relative to the background, which raises the contrast of emission regions. Hydrogen-beta emission is generally weaker than hydrogen-alpha and doubly ionized oxygen in the same nebulae, so the gain on many targets is smaller than that of an OIII filter. The glass carries a multi-layer interference coating on one side and an anti-reflection coating on the other, which together set the passband and limit reflections. The passband also shifts the color of stars toward green.

Suitable targets include bright emission regions such as the Orion Nebula and the Rosette Nebula, viewed through a telescope of moderate aperture under dark skies. Under light-polluted skies the filter helps less, because it does not reject the full spectrum of artificial light. On galaxies, star clusters, and reflection nebulae the filter reduces brightness without adding detail, since those objects do not emit mainly at 486 nm. Compare the view with a UHC or OIII filter on the same target before choosing it, since those filters often show more of an emission nebula. Keep the filter in its case when not in use to protect the coatings from dust and scratches.

About this configuration

This listing covers one configuration of the Pellucid Lucent H-beta narrowband filter 1.25 in, defined by its grade, coating, case, and edition year. 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 Lucent line, which suits imaging with long focal lengths. Hard-sputtered layers keep their passband stable over time, which matters if you compare images taken years apart.

The filter ships in a clear plastic case that keeps dust off the glass between sessions. This is the 2023 edition of the Lucent line, the earliest version that is still listed 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 1.25 in threaded cell
• Plastic storage case
• Test report with measured transmission curve
• Plastic storage case

Compatibility notes

• Threads into 1.25 in eyepieces, diagonals, and filter wheels (M28.5 x 0.6).
• Most useful on emission nebulae under moderately dark skies.