Baader Filters H-alpha/OIII/SII CMOS Narrowband 31mm (70894)

The H-alpha filter passes light at a wavelength of 656 nm. It is the best choice for narrowband H-alpha astrophotography, offering high-contrast imaging and revealing rich details of nebulae, even in areas with strong light pollution.

The OIII filter is a narrowband filter designed for nebula observation. It allows a 3 nm bandwidth of light centered on a wavelength of 500 nm, corresponding to OIII emission lines, while blocking all other light.

The SII filter is a narrowband filter that passes light at a wavelength of 672 nm with a bandpass of 3 nm. It is specifically designed for nebula photography and is suitable for imaging 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 to replicate 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): 656.3 (H-alpha), 500.7 (OIII), 671.7 (SII)
Half-Value Width (nm): 6.5

Frame
Type: Ring
Mount Material: Aluminium
Coating: Reflex-Blocker™

Appropriate for Telescopes
Aperture Ratio Range: f/10 to f/3.5

Filter Thickness
Thickness (mm): 2

Filter Size
Size (mm): 31

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

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