Chroma H-Alpha 3nm Filter 2" Unmounted

Chroma 3nm H-alpha filters are essential for imaging nebulae and other objects which are rich in ionised hydrogen. At 656.3nm, a narrow-band emission filter is required to separate H-alpha from the SII doublet (671.6nm and 673.1nm).

About Chroma

Chroma Technology is an employee-owned company based in Vermont, USA. Chroma manufacture the highest quality astronomy filters with durable, sputtered hard coatings using single substrates of the best glass, eliminating the need for laminations. All primary filter coatings are applied on the front surface and anti-reflection coatings on the rear surface to prevent ghosting and to maximise transmission. Chroma astronomical filters are used worldwide in research and amateur applications. 

Highly precise and accurate, the passbands of Chroma filters remain spectrally stable and do not drift in response to extreme temperature fluctuations or changes in humidity.

All Chroma filters may be used with focal ratios of f/4 or slower. For optics faster than f/4 then due to the spectral shift, we recommend using 5nm filters instead.

Features of the Chroma H-Alpha Filter

• CWL: 656nm, Bandwidth: 3nm
• Durable sputter coatings
• Parallelism: <30 arcsec
• Thickness: 3.0 +/-0.05mm
• Filters designed for use with CCD and for f/4.0 or slower
• Transmitted wavefront better than 0.25 waves/inch
• No reflections leading to image distortions or ‘back reflections’