Baader Filters SII CMOS Ultra-Narrowband 2" (70889)

The SII filter is a narrowband filter that passes light at a wavelength of 672 nm with a bandpass of 3 nm, making it ideal for nebula photography. It is specifically designed for capturing most emission nebulae, planetary nebulae, and supernova remnants.

If you want to achieve the iconic look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” in the Eagle Nebula (Messier 16), the SII filter is an excellent addition to your collection after H-alpha (H-a) and OIII filters. Like the H-a filter, the SII filter is a deep red filter near 672 nm. Together, H-a, OIII, and SII filters enable tri-color narrowband imaging, providing that Hubble-like appearance for many emission nebulae. Additionally, these filters allow imaging even when the moon is up, ensuring your equipment remains active without long periods of downtime.

Specifications

Capacity
Central Wavelength (nm): 671.7
Half-Value Width (nm): 4

Frame
Size: 2"
Mount Material: Aluminium
Coating: Reflex-Blocker™

Connection to Telescope
Size: 2"
Aperture Ratio Range: f/10 to f/3.5

Filter Thickness
Thickness (mm): 2

General Information
Type: Filters
Build Type: Line filter
Series: Ultra-Narrowband

Area of Application
Useful for Photographs: Yes
Visually Useful: No
Twin Stars: No
Moon & Planets: No
Nebulae & Galaxies: Yes