Brightwell Nightline UHC nebula filter 1.25 in

Specifications

Description

The Nightline UHC is an ultra-high contrast nebula filter in a 1.25 in threaded cell. It passes a band about 25 nm wide that covers the doubly ionized oxygen lines at 496 and 501 nm and the hydrogen-beta line at 486 nm, and it passes the hydrogen-alpha line in the deep red. It blocks most other visible light, including much of the glow from artificial lighting.

Emission nebulae shine at those specific wavelengths, while the sky background glows across the spectrum. By blocking the background and passing the nebula's light, a UHC filter raises the contrast between the two. The nebula does not get brighter, but the sky around it gets darker, so faint outer regions become visible.

Good targets include the Orion Nebula, the Lagoon and Trifid nebulae, the Swan Nebula, the North America Nebula in a wide-field telescope, and planetary nebulae such as the Ring and the Dumbbell. The effect is strongest in telescopes of 100 mm aperture or more and under moderately dark skies.

A UHC filter does not help with galaxies, star clusters, or reflection nebulae, which shine in a broad range of colors. On those targets it simply dims the view. It also makes stars appear greenish, since the passband sits in the blue-green part of the spectrum.

The filter screws into the barrel of any 1.25 in eyepiece or the nosepiece of a 1.25 in diagonal. The glass is coated on one side with the multi-layer interference stack and on the other with an anti-reflection layer.

For many observers, a UHC filter is the first nebula filter to buy, because it works on a wide range of emission and planetary nebulae.

About this configuration

All configurations of the Brightwell Nightline UHC nebula filter 1.25 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 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. The 2023 edition uses the same coating design as later years, with small differences in the cell markings. Check the size in the specifications against your eyepiece barrels, star diagonal, or filter wheel before you choose.

What's in the box

• UHC filter in 1.25 in threaded cell
• Plastic storage case
• Plastic storage case

Compatibility notes

• Threads into 1.25 in eyepieces, diagonals, and filter wheels (M28.5 x 0.6).
• Most effective in telescopes of 100 mm aperture and larger.