Askar H-Alpha 7 nm 2" Narrowband Filter

The Askar H-Alpha 7 nm 2" filter is a superior-grade filter designed to capture the red light emitted by ionized hydrogen atoms with a wavelength of 656.3 nm. This filter is particularly crucial when photographing emission nebulae, as it enables the precise registration of this important spectral line.

With an impressively narrow half-bandwidth of only 7 nm, the Askar H-Alpha filter effectively eliminates the undesirable components from sodium and mercury lamps while providing high transmission for the Hα spectral line. This spectral line is widely recognized as one of the most significant aspects of astrophotography.

It is important to note that the Hα filter is primarily recommended for astrophotography purposes and not intended for visual observations.

Key Features of the Askar H-Alpha 7 nm 2" Filter:

Bandpass Filter: This filter is designed as a bandpass filter, allowing maximum transmission for radiation with a wavelength of 656.3 nm.

Narrow Half-Width: The filter boasts an extremely narrow half-width of the transmitted band, measuring at FWHM = 7 nm. This characteristic ensures precise filtration and optimal results.

OD4 Optical Density: With an equivalent optical density of OD4, the Askar H-Alpha filter guarantees exceptional light pollution reduction, reaching an impressive effectiveness level of 99.99%.

Technical Specifications:

• Filter Type: Bandpass Filter
• Filter Diameter: 2"
• Filter Thickness: 1.85 ± 0.1 mm
• Filter Shape: Round
• Transmitted Bands: Hα (656.3 nm)
• Peak Permeability Location (CWL): 656.3 ± 1 nm
• Half Bandwidth: 7 ± 1 nm
• Maximum Transmission: >90%
• Blocked Bands: Mercury Lamps (435.8 nm, 546.1 nm, 577 nm, 578.1 nm), Sodium Lamps (598 nm, 589.6 nm, 615.4 nm, 616.1 nm)
• Light Pollution Blocking Efficiency: >99.99%
• Equivalent Optical Density for Blocked Lines: OD4 (200 - 1050 nm)
• Surface Quality Index: 60/40
• Parallelism: 30"
• Light Incidence Angle: 0 - 8°
• Frame Finish: Matte Black, Anodized
• Holder Thread: M48x0.75

Included in the Set:

• Askar H-Alpha 7 nm 2" Filter

Warranty:

The Askar H-Alpha 7 nm 2" Filter is accompanied by a 24-month guarantee, providing peace of mind for your astrophotography endeavors.