Optolong narrowband Oxygen O-III 18nm 2.0″

1.  Optolong OIII Introduction

Optolong narrowband OIII filter is designed for nebula observation allowing 18nm bandwidth of light centered on a wavelength of 500nm through, which corresponds to OIII emission lines, 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).

OIII emits 495.9nm and 500.7nm and it is a blue-green colored filter. Many of images of planetary nebula and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colors, looking like an RGB image.

Main Use

Suitable for visual observation on most emission nebulae, planetary nebulae and supernova remnants.

Suitable for viewing on bright nebulae like M42 Orion Nebula in heavy light pollution.

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

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.

2. Optolong OIII Spectrum and Characteristic

• 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 RED line shows the transmission of the OIII filter. Green line shows the emmission of nebula. The artifical emission lines are shown in ORANGE.