Optolong H-Alpha Narrowband (7nm) Filter - 31mm Unmounted

Latest Version - Higher contrast and coating enhancements.

The Optolong H-Alpha 7nm filter is the most popular narrowband filter in the range allowing 7nm bandwidth of light centered on a wavelength of 656nm through. This filter does an excellent job of blocking out other wavelengths of light specifically artificial sources of light pollution including mercury vapour, high and low pressure sodium vapour lights and unwanted natural light caused by neutral oxygen emission in our atmosphere (skyglow).

This filter can help increase contrast and reveal subtle nebula details in your images. Suitable for imaging faint emission nebula in the H-Alpha line even in full moonlight or areas of high light pollution.

Warning - Optolong filters are not designed to be used for solar observation. Do not look at the sun through this filter as it will cause permanent eye damage.

Transmission Chart

Red Line: H-alpha, 7nm centred at 656.3nm.

Blue Line: SII, 6.5nm centred at 671.6nm.

Green Line: OIII, 6.5nm centred at 500.7nm

Technical Data

• Schott substrate material
• Thickness 2.0 mm
• Surface Quality: 60/40 (Refer to MIL-O-13830)
• Fine-optically polished to ensure accurate 1/4 wavefront and <30 seconds parallelism over the both surfaces
• 95% transmission at passband

• Infrared wavelength 700-1100nm cut-off

• Precision off-band blocking

Coating Parameter

• Multi-layers anti-reflection coating
• Non-cementing optical substrate coating
• 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
• Planetary rotation system offers precision and homogeneity of coatings ensuring high value on transmission of pass-band and Optical density of off-band

Filter Cell

• Ultra-thin filter cell minimise vignetting by maximise possible clear aperture (clear aperture is 26mm for 1.25”; 45mm for 2”)
• Aerometal Material | Precise CNC Machining | Sand Blasting Process | Black Anodised Finish | Extinction Treatment to Prevent Reflection | Laser Engraving No Fading

Sample Images

About Optolong

While Optolong is a relative newcomer to the astronomy industry, they are no strangers to optics and filters. Optolong is a division of Yulong Optics Company, a high tech company specializing in optical filter design and production. Their products include bandpass filters, flourescence filters, edge filters, longpass and shortpass filters, beam splitters, anti-reflection coatings, optical mirrors and, of course, astronomical filters.

Established in 1999 and based in Kunming City, China, Optolong/Yulong provides nearly 2000 types of optical filter coatings annually to customers worldwide in a wide variety of industries and applications.