Baader Ultra-Narrowband 3.5nm H-alpha Filters are precision grade for f/10 to f/3.5 optical systems.
Designed for imaging the extremely narrow 3.5nm H-alpha band. The enforced contrast results in much fainter stars providing more signal in the fainter nebula details with the central wavelength of the filter being 656.3nm.
The manufacture of such ultra-narrow filters requires extreme coating homogeneity and very high center-wavelength (CWL) precision. Each filter is planeoptically polished and hard coated.
Filter sizes available:
- 1.25" (2mm glass thickness)
- 31mm unmounted (2mm glass thickness)
- 36mm unmounted (2mm glass thickness)
- 2" mounted (2mm glass thickness)
- 50.4mm round (2mm glass thickness)
- 50x50mm square (2mm glass thickness)
- 65x65mm square (2mm glass thickness)
Important: These filters are intended only for imaging use. They are not suitable for any form of solar filtration. Please see our solar filter section for filters designed specifically for safe solar use.
Below is the real filter-spectrum, taken with an MPI-DADOS-Spectrograph. Comparision with the solar-spectrum (including solar absorption lines).