copy of Filter ANTLIA SII 7nm PRIME model 36mm circular filter without mount

All you need to know about PRIME Antlia 7nm OIII filters

The Antlia 7mm OIII filter is suitable for imaging Oxygen-3-rich planetary nebulae and supernova afterglows. The 7 nm bandwidth (centered on the OIII line at 500.7 nm) gives PRIME filters a wider bandwidth than the EDGE range. Therefore, PRIME filters let a little more signal through... but a little more light pollution. The finer bandwidth allows deep sky imaging even under very difficult light pollution conditions, and greatly increases the contrast of objects under very dark skies. A large proportion of light pollution lines, especially from mercury vapor and sodium lamps, are eliminated.

Antlia PRIME narrow band filters are designed to bring out the faintest details of nebulae by suppressing unwanted wavelengths from the sky background. The narrower the bandwidth, the more effective the filter. The transmission of the filter reaches 91% at 500.7 nm. The optical density outside the transmission area is OD4 (0.01%), 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 cutoff slope, the greater the contrast between the OIII signal and the perfectly black background sky. In addition, a sharp cut-off minimizes halos around bright stars.

Antlia conductsextremely 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 require perfectly homogeneous substrates and uniform thicknesses; deviations from specifications should not exceed 0.05 mm.

Applications and performance

• Narrow bandwidth of 7 nm, designed for astronomical imaging of planetary nebulae and supernova afterglow, whatever the sky quality
• Can be combined with Antlia 7nm SII and H-Alpha filters for SHO imaging in the Hubble palette
• Sharp cut-off of unwanted lines around OIII. Transmission is 91% at 500.7nm, which increases the contrast of objects with OIII emission.
• Antlia EDGE narrowband filters are compatible with instruments at F/d >2 with slight signal loss.
• All Antlia filters have blackened edges to suppress stray reflections.

Technical specifications:

• Glass type: Schott optical glass
• Surface quality: 60/40 (according to MIL-O-13830)
• Mounting diameter: 36mm circular without mount
• Substrate thickness: 2 mm
• Transmission: 91% at 500.7nm OIII line
• Treatments: 2-sided polished filter with an accuracy of λ/4
• Coating: multilayer and anti-reflective on 2 sides