[IMPROVED] OIII 6.5nm narrowband filter
Over the past year or more Optolong has put significant effort into solving the problem what always annoyed astronomers. Our goal was to reduce halos caused by our filters to a level were it would not noticeably affect imaging. By making a number of modifications in the coating technique, we finally made it.
  • Description

  • Specification

1. Optolong OIII 6.5nm Narrowband Introduction

Extra Narrowband OIII-CCD 6.5nm filter is designed for nebula observation allowing 6.5nm 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.

  • Suitable for visual observation on emission nebulae, planetary nebulae and supernova remnants.
  • Hubble look of images can be made by the combination of H-alpha, OIII-CCD and SII-CCD, such as the famous “Pillars of Creation” (M16 Eagle 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.


2. Referance Spectrum

How to read the chart?

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

▲The vertical axis is transmission in %.

▲The GREEN line shows the transmission of the OIII6.5nm filter. The H-Alpha7nm line is shown in  RED. And the SII6.5nm line is shown in BLUE.


3. Improved OIII6.5nm Narrowband Filter Feature


Optolong OIII6.5nm Filter Specifications Applicable Model Unit Price in US$
1.25" /1 1/4" mounted) M28.5*0.5 $159
2" mounted M48*0.6 $255
31mm unmounted CCD filter wheel $189
36mm unmounted CCD filter wheel $195





4. Manufacturing Technology

⭐High-precision grinding and polishing to make sure the substrate parallelism is greater than 30" and the surface accuracy is better than λ/4 ;

⭐Purified water ultrosonic clearning is aim to effectively remove impurities and dust from the substrate surface.

⭐Electron-beam gun evaporation with Ion-assisted deposition coating technology for durability and resistance to scratching, as well as stability on CWL(central wavelength) no deviation affected by temperature change; IAD not only consolidates membrane compactness, increases film firmness, but also changes vacuum coating material characteristics.

⭐Planetary rotation system offers precision and homegeneity of coating ensuring high value on transmission of pass-band and Optical density of off-band;

⭐Non-cementing optical substrate coating;

⭐Quality Control: each filters is examined by Spectrophotometer for spectrum characteristic, and Laser Interferometer for surface accuracy.



5. Packing

2019 NEW package

※Note:We are now in the transition from the old to the new packaging style, ship is random.



6. Filter Performance

I. IC1805, shot by Francesco Battistella

After months of work, this is the first image taken from my new observatory! by Francesco Battistella
The Heart Nebula in Hubble Palette technique -IC1805 
Using improved Optolong's narrowband filters and the results were excellent.



II. Going Starless on IC 5068, shot by Chuck's Astrophotography

Chuck's Astrophot Going Starless on IC 5068 
IC 5068 seemed like a very dense cloud and an interesting target to see how removing the stars would look with it. It's captured with Optolong improved narrowband filters.
Integration: 16.8 hours



III. Meet NGC7822, Shawn Nielsen

Meet NGC7822. This is 29 hours of data, 
 collected over 6 clear nights. This is a Hubble palette image (false colour).
NGC 7822 is a young, star-forming region in the constellation of Cepheus.
Shot with 
 improved narrowband filters SHO6.5nm


IV. Meet Sh2-132, by Chuck's Astrophotography/ Chuck Ayoub

Sh2-132, also called the Lion Nebula, is a faint emission type nebula on the Cepheus/Lacerta border. It is estimated to be about 10,000 to 12,000 light years away from Earth.
I captured it in narrowband filters and processed it in the Hubble Palette. Here are the specs:
Target: Sh2-132
Imaging Telescope: Orion ED80T CF
Imaging Camera: ZWO ASI1600MM Pro
MoonLite 2.5" Focuser with Motor Auto-Focus
Focal Reducer: Orion .8 Reducer
Mount: Sky-Watcher EQ6-R Pro
Polar Alignment: QHYCCD PoleMaster
Optolong Ha: 142x240" (gain: 139, offset: 21)
Optolong OIII: 157x240" (gain: 75, offset: 15)
Optolong SII: 135x240" (gain: 139, offset: 21)
Integration: 28.92 hours
Guide Scope: ZWO 60mm Guide Scope
Guide Camera: ZWO ASI224MC
Guide Software: PHD2
Calibration Frames:
Darks: 50, Bias: 200, Flats: 50
Capture software:
Sequence Generator Pro (SGP)
Stacking software: PixInsight
Post Processing: PixInsight, PhotoShop
Dew Shield, Dew Heater Strip


VI. Rosette Nebula, by Andrea Andreotto Maggi

Rosette Nebula
Telescopio quadrupletto 70 mm f5 #Artesky
Camera Asi 1600 MM pro
21 Light HA 600 sec gain 0
18 Light OIII 600 sec gain 0
14 Light SII 600 sec gain 0
Filtri Optolong



VII. Eta Carinae Nebula (NGC 3372) , by Fabian Rodriguez

NGC3372 comparison image was shot with Optolong upgraded SII 6.5nm, OIII 6.5nm and H-alpha 7nm filter, the upper photo was shot with other brand SHO filter.
9x900" Ha 
6x900" OIII
6x900" SII
Shot in same equipment and data.
Eta Carinae Nebula (NGC 3372) is one of the largest and brightest hidrogen cloud in the sky, quite a good object to test the narrowband filters.



Warm Reminder:

  • About Color: The package may different due to different photography environment, lighting. What you have seen in the picture is absolutely what it is being. You might feel somewhat of color different subject to the monitor and camera, please refer to the material item.
  • About Coating: The interference items will show rich colors in different light environment, which is normal phenomenon.
  • About Product Object: Product specifications may change to improve product quality, and that updates to the specifications will be published as soon as possible.
  • About Product Overview: Please note that H-Alpha 7nm filter with same design, same raw material . Size is the only difference.

Optolong OIII6.5nm features 4 sizes:

★1.25"(1 1/4" mounted), 2" mounted for eyepiece

★Round 31mm unmounted, 36mm unmounted for filter wheel