Astronomik H-Alpha 6nm CCD 31mm Filter

Astronomik H-alpha 6nm CCD filter 31mm

If you are an astrophotographer looking to push your imaging of emission nebulae, planetary nebulae or active star-forming regions to the next level, the Astronomik H-alpha narrowband filter with a 6nm bandwidth is the tool that will transform your images. Designed specifically for CCD cameras, this filter reliably isolates hydrogen H-alpha emission at a wavelength of 656.3nm while effectively suppressing light pollution, city glow and natural airglow.

Outstanding optical performance

At the heart of this filter is its exceptionally narrow passband of just 6nm (FWHM - full width at half maximum), which delivers extremely high contrast between emission structures and the background sky. At the same time, the filter maintains a transmission rate of 96%, which is an outstanding value for a narrowband filter - you avoid unnecessarily long exposures and your sensor receives the maximum possible signal from the target wavelength band.

Choosing the right bandwidth

Selecting the correct filter bandwidth is a key decision when building your astrophotography system. Wider filters (12nm or more) are more forgiving of precise thermal stability and are somewhat less sensitive to the angle of incoming light, but they allow more unwanted background through. A 6nm filter, by contrast, offers dramatically better rejection of light pollution and natural airglow, while still maintaining sufficient mechanical tolerance for most available optical systems. It is an ideal choice for both suburban observers and experienced astrophotographers at dark-sky sites who want to achieve maximum contrast in emission structures.

Optimised for modern cameras

The Astronomik H-alpha 6nm CCD filter is fully optimised for modern monochrome CCD and CMOS cameras. The filter coating is applied directly to the substrate without the use of adhesives, ensuring long-term stability of optical properties and resistance to moisture and mechanical stress. The filter can be used in combination with OIII and SII filters to create narrowband composites in the Hubble palette (SHO) or bicolor techniques (HA+OIII).

Design and compatibility

The filter is housed in an aluminium frame with a diameter of 31mm in an unmounted "ring" design (no thread), which integrates easily into standard filter drawers or filter wheels. The 31mm unmounted format is intended primarily for users of filter wheels with cells for unmounted filters of this diameter - most commonly filter wheels for APS-C format cameras or smaller.

This filter is ideal for astrophotographers working with systems such as ZWO ASI, QHY or Atik who demand maximum performance when imaging emission nebulae, even from locations with heavy light pollution. Thanks to the high 96% transmission, the filter is also effective when used on refractors or Newtonian telescopes with fast focal ratios, where the angular characteristics of the filter need to be taken into account.

About Astronomik

Astronomik is a German manufacturer with a long tradition and a clear philosophy: every filter must meet strict optical standards verified by interferometric and spectroscopic testing. Astronomik filters are popular among both amateur and professional astrophotographers worldwide, thanks to consistent manufacturing quality, careful bandwidth control and excellent mechanical precision of the frames. Choosing Astronomik is not just buying a filter - it is an investment in reliable optical equipment that will perform accurately and stably for many years to come.

Key specifications