Optolong Narrowband H-Beta filter

Opotlong narrowband H-beta filter is designed for nebula observation allowing 12nm bandwidth of light centered on a wavelength of 486nm through, and reducing the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow). H-beta emits 486nm and it is a blue-colored filte.

Main Use

Use with a large aperture telescope under clear and dark viewing conditions with good seeing.

Suitable for viewing on the faint and elusive Horsehead Nebula and California Nebula.

Narrowband filter do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTER. You would be BLIND if you fail to observe the warning.

Technical Specifications

Substrate: Optical glass
Thickness: 1.85mm
Tave: T>80%
Blocking range: 400-700nm
Blocking depth: light pollution line blocking >99%
Surface quality: 60/40
Transmitted Wavefront RMS: λ/4
Parallelism: 30s

How to read the chart?

▲The horizontal axis is the Wavelength in Nanometers(nm).

▲The vertical axis is transmission in %.

▲The WHITE line shows the transmission of the H-Beta filter. Green line shows the emmission of nebula. The artifical emission lines are shown in ORANGE.