Filter ANTLIA H-ALPHA 4.5nm EDGE model 36mm circular unmounted filter

All you need to know about Antlia's 4.5 nm EDGE H-alpha filters

Antlia's 4.5 mm H-alpha (Ha) filter is suitable for imaging diffuse nebulae, planetary nebulae and Ha-rich supernova afterglow. The 4.5 nm bandwidth is centered on the H-alpha line at 656.3 nm. The thinness of the bandwidth allows deep sky imaging even under very difficult light pollution conditions, and greatly increases the contrast of objects under very dark skies. All light pollution lines, including those from mercury vapor and sodium lamps, are eliminated.

Antlia EDGE narrow band filters are designed to bring out the faintest details of nebulae by removing unwanted wavelengths from the sky background. The narrower the bandwidth, the more effective the filter. Filter transmission reaches 94% at 656.3 nm. The optical density outside the transmission zone is OD5 (0.001%), which provides an excellent signal-to-noise ratio and a clear cut-off of the other lines. The clear cut-off of the signal outside the transmission zone is an important parameter because it determines the quality of the filtration. The steeper the cut-off slope, the higher the contrast between the H-alpha signal and the perfectly black background sky. In addition, a sharp cut-off zone minimizes halos around bright stars.

Antlia conducts extremely strict quality control during the manufacturing process. Each filter is tested and measured to ensure that it meets the high performance requirements of the specifications. Tight tolerances force the use of perfectly homogeneous surfaces and uniform thicknesses; deviations from specifications should not exceed 0.05 mm.

Applications and performance

• Very narrow bandwidth of 4.5 nm, designed for astronomical imaging of diffuse nebulae, planetary nebulae and supernova remnants, regardless of sky quality.
• Possibility of association with SII and OIII Antlia 4.5nm filters to obtain SHO images in the Hubble palette
• Sharp cut of unwanted lines around H-alpha. Transmission is 94% at 656.3 nm and increases the contrast of H-alpha emitting objects.
• Antlia EDGE narrowband filters are compatible with instruments at F/d >3 with slight signal loss
• All Antlia filters have blackened edges to eliminate unwanted reflections.
• This filter is not suitable for imaging objects that do not emit any H-alpha signal, such as galaxies. However, adding an H-alpha channel to an LRGB image of a galaxy will highlight the nebulae it contains.

Technical Specifications

• Glass type Schott optical glass
• Surface quality: 60/40 (according to MIL-O-13830)
• Material thickness: 2 mm
• Transmission: 90% transmission in the H-alpha line (656.3 nm)
• Treatments: filter polished on both sides with λ/4" accuracy
• Multilayer and anti-reflective treatments on both faces