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Astronomik SII 6 nm CCD Filter - 1.25" - SII6-1

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SKU: ASF-SII6-1

Astronomik SII 6 nm CCD Filter - 1.25"


  • This SII CCD Filter from Astronomik comes mounted in a round 1.25" threaded cell for the express purpose of astrophotography
  • Designed with the highest technical standards in mind to enable peak optical performance for deep sky imaging applications with your CCD camera
  • Permits ionized sulfur (SII) light to be transmitted while simultaneously cutting off the entire remainder of the visual spectrum plus IR
  • Approximate FWHM bandwidth of 6 nm
  • Best-suited for imaging planetary nebulae and supernova vestiges
  • German-made for superior optical quality!


More About the Astronomik 1.25" SII 6 nm CCD Filter


For CCD astrophotography operations, this 1.25" SII 6 nm CCD Filter from Astronomik is the ideal narrowband filter. It has a smaller full width at half maximum (FWHM) of 6 nm to enable higher contrast gain than you would get from the 12 nm filter when also factoring in a typical 96% transmission given that all unwanted light from alternate wavelengths from UV up to IR is blocked. This results in an especially dark background. While you may experience transmission reductions and chromatic distortions with other filters, these only occur with Astronomik filters when exceptionally bright 1:2 and above aperture ratios are involved.

Astronomik SII CCD filters highlight the contrast between objects that emit in the ionized sulfur (SII) line and the background sky. This filter also serves as an excellent filter for combating light pollution as it offers total suppression of artificial sources of light such as mercury and sodium-vapor street lamps, a common cause of light pollution. The Astronomik SII CCD Filter's high quality substrate enables you to see razor sharp stars identical to those you would see with the telescope you typically use.

All superfluous wavelengths in the visible and IR bands of the spectrum are completely obstructed with the Astronomik 1.25" SII 6 nm CCD Filter. Parfocal with all other Astronomik filters and diffraction limited to keep the optical performance of your telescope from degrading. The coatings on this filter provide remarkable protection from scratching as well as high humidity and aging effects. The Astronomik 1.25" SII 6 nm Filter is delivered in a durable, high-quality plastic filter case.

Transmission Specifications


  • Typical 96% transmission in the SII line
  • Offers complete blockage of unwanted light from UV up to IR