Pellucid Spectra UHC nebula filter 2 in, premium grade

Specifications

Description

The Spectra UHC is an ultra-high contrast nebula filter in a 2 in threaded cell, made on polished optical glass. Its 22 nm passband covers the hydrogen-beta and doubly ionized oxygen lines between 486 and 501 nm, with peak transmission of about 95 percent, and it also passes the hydrogen-alpha line.

The narrow passband darkens the sky background strongly while keeping most of the light from emission nebulae. Under suburban and rural skies, the Spectra UHC shows the outer loops of the Orion Nebula, the dark lanes in the Lagoon Nebula, the Eagle Nebula around M16, and the full shape of the North America Nebula in wide-field telescopes.

The polished substrate keeps the filter optically flat, so it adds no visible distortion at high magnification. That matters when you observe small planetary nebulae, such as the Cat's Eye or the Eskimo, at 200x or more, where the filter can show shells and structure around the bright inner regions.

The multi-layer coating is hard-sputtered on one side, with anti-reflection coatings on both faces. The 2 in cell threads into eyepieces, diagonals, and filter wheels with the standard M48 thread.

Like all nebula filters, the Spectra UHC dims stars and gives them a greenish tint, and it does not help with galaxies or star clusters. Keep it for emission and planetary nebulae, and observe other targets without it.

The 2 in size suits telescopes with 2 in focusers, where it can stay in the diagonal while you change eyepieces.

About this configuration

This listing covers one configuration of the Pellucid Spectra UHC nebula filter 2 in, defined by its grade, coating, case, and edition year. 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. The hard-sputtered coating resists scratches and humidity, so the filter tolerates cleaning better over the years.

The filter ships in a clear plastic case that keeps dust off the glass between sessions. This is the 2023 edition of the Spectra 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

• UHC filter in 2 in threaded cell
• Padded storage pouch
• Plastic storage case

Compatibility notes

• Threads into 2 in eyepieces, diagonals, and filter wheels (M48 x 0.75).
• Most effective in telescopes of 150 mm aperture and larger under rural or suburban skies.