The Antlia SII Pro narrowband filter is optimised for a bandwidth of 3nm. As the bandwidth becomes narrower, the 3nm Pro narrowband filters improve the contrast of emission objects by reducing unwanted background signal. The Antlia SII 3nm Pro filter is designed to provide 88% transmission at the 671.6nm line, providing maximum signal and well-defined nebula structures.
Conventional wider narrowband filters cause a significant loss of transmission due to the strong "centre wavelength shift". With its high transmission, the SII 3nm Pro narrowband filter is specially designed for use with long focal lengths and fast optical systems. Blue shift data shows that Antlia 3nm Pro filters can be used on almost all systems with a focal length of f/3 with only minimal loss of emission signal and meet the requirements of fast optics such as Hyperstar and RASA. The neutral density of OD5 (=0.001%) results in an excellent signal-to-noise ratio and an effective cut-off rate to minimise interference from other wavelengths. Improved, sharp cut-off properties reduce halos around bright stars very effectively.
