Brightwell Nightline Skyglow filter 2 in

Specifications

Description

The Nightline Skyglow is a broadband light-pollution filter in a 2 in threaded cell. It blocks the emission lines of low-pressure and high-pressure sodium lamps and of mercury-vapor lamps, while passing most of the blue-green and red light where many deep-sky objects shine.

Under suburban skies lit by older street lighting, the filter darkens the background noticeably and improves the contrast of emission nebulae, planetary nebulae, and to a smaller degree galaxies. Its broad passband keeps the view natural, with stars close to their normal colors.

Modern LED street lighting emits a continuous spectrum, so a broadband filter blocks less of it. Under LED-lit skies, the Nightline Skyglow still gives a modest improvement on nebulae, but a narrower UHC or OIII filter usually works better for those targets. Expectations matter: no filter turns a city sky into a dark site.

For photography, the filter reduces the orange cast that sodium lighting adds to images, which simplifies color balancing. It suits one-shot color cameras and DSLR cameras with refractors and reflectors.

The filter threads into the barrel of any 2 in eyepiece or the nosepiece of a 2 in diagonal. It can also sit in front of a camera adapter in imaging setups that accept 2 in filters.

The glass is coated with a multi-layer interference stack on one side and an anti-reflection coating on the other, which keeps halos around bright stars low.

The Nightline Skyglow suits observers in suburbs who want one filter for general use, both at the eyepiece and with a camera.

About this configuration

The Brightwell Nightline Skyglow filter 2 in is offered in several configurations, and the notes below describe what this particular one includes. 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.

A padded pouch is easy to open with cold fingers, which helps when you swap filters during a session. This is the 2023 edition of the Nightline 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

• Light-pollution filter in 2 in threaded cell
• Plastic storage case
• Padded pouch

Compatibility notes

• Threads into 2 in eyepieces, diagonals, and camera adapters (M48 x 0.75).
• Most effective against sodium and mercury lighting; less effective against white LED lighting.