Brightwell Nightline Skyglow filter 2 in, observatory grade

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 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 Nightline line, which suits imaging with long focal lengths. With anti-reflection layers on both sides, less light bounces between the filter and the eyepiece or camera sensor.

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

• Light-pollution filter in 2 in threaded cell
• Plastic storage case
• Test report with measured transmission curve
• 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.