Pellucid Spectra UHC nebula filter 2 in

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

All configurations of the Pellucid Spectra UHC nebula filter 2 in share the same filter glass design; the options change the grade, the coating, and the case. The standard grade uses the same coating design as the higher grades, with wider tolerances on flatness. Standard grade glass suits visual observing at low and medium magnification. The standard coating is applied to the filter side of the glass, with a single anti-reflection layer on the back.

The padded pouch protects the filter from knocks and fits in a jacket pocket at the telescope. 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
• Padded pouch

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.