Optolong Filters H-alpha 7nm 2" (83198)

Optolong Filters H-alpha 7nm 2" (Model 83198)

The Optolong H-alpha 7 nm 2" filter is a high-performance narrowband line filter designed for astrophotography and visual observation of deep-sky objects. It isolates the hydrogen-alpha emission line at 656 nm, significantly enhancing contrast and revealing fine nebular structures, even under strong light pollution. By blocking unwanted artificial and natural skyglow wavelengths, it delivers sharper images with improved detail and background darkness. This filter is particularly well suited for capturing emission nebulae.

Optical Performance
Central wavelength: 656.3 nm
Bandwidth (FWHM): 7 nm
Transmission: 85%
Surface accuracy: 1/4 wave
Optical coating: Multi-layer coating

The filter allows only a narrow 7 nm band of light centered at 656 nm to pass through, while effectively reducing transmission of unwanted wavelengths. These include light from mercury vapor lamps, high- and low-pressure sodium lamps, and natural atmospheric oxygen emissions responsible for skyglow.

Mechanical Specifications
Filter diameter: 2"
Filter thickness: 2 mm
Clear aperture: 45 mm
Mount material: Aluminum
Telescope connection: 2"

Type and Application
Type: Line filter
Primary use: Astrophotography
Visually useful: Yes
Suitable for nebulae and galaxies: Yes
Suitable for twin stars: No
Suitable for Moon and planets: No