Optolong Hydrogen-Alpha 7nm Filter

H-Alpha 7nm filter is the most popular narrowband filter, allowing 7nm bandwidth of light centered on a wavelength of 656nm through. It reduces 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. sky glow). This is the best choice of narrowband H-alpha astrophotography filter for highest contrast and revealing subtle nebula details.

• Fine-optically polishing for double-sides-- Ensure accurate λ/4 wavefront and <30 seconds parallelism over the both surfaces
• Ultrasonic wave cleaning substrate with purified water to remove impurities and dust effectively
• IRO source assisted coating - For durability and resistance to scratching, as well as stability on CWL (central wavelength).  No deviation from temperature change.
• Constant stringent quality testing processes - Each filter is tested by spectrophotometer and laser interferometer testing spectrum and wavefront to ensure market filter is qualified product
• Optolong will spare no effort to serve our customer with outstanding quality products and best service!

Specifications

CWL(center of wavelength): H-Alpha 656.3nm
FWHM: H-Alpha7nm
Tpeak: <85%
Optical Density: OD 3
Surface Quality: 60/40
Transmitted Wavefront RMS: λ/4
Parallelism(arc sec): 30s