Astronomik H-alpha CCD 12nm 2″ Filter

Astronomik H-alpha CCD 12nm 2″ Filter

The Astronomik H-alpha CCD 12nm filter is a dedicated narrowband filter for astrophotography of hydrogen emission nebulae. It works equally well from heavily light-polluted city locations and from dark-sky sites. The filter dramatically increases contrast between objects glowing at the H-alpha emission line (656 nm) and the night-sky background. Fine details in emission regions that would otherwise be lost in artificial sky glow become clearly visible. This filter is designed exclusively for photographic use with cooled CCD cameras, CMOS sensors, and DSLR cameras - it is not suitable for visual observation.

Why 12nm Bandwidth?

A 12nm bandpass represents the best balance between light pollution suppression and compatibility with a wide range of optical systems. Narrower filters block more sky background, but they also reduce transmission significantly and make it harder to find guide stars. With cooled CCD cameras in large cities, the limiting factor is usually camera dark current rather than sky background brightness - so an even narrower filter will not reveal more detail in the object. The 12nm H-alpha filter achieves near 100% transmission at the target wavelength. This makes it compatible with fast optical systems from f/2.8 to f/15, so it suits both small-aperture telescopes and large-format astrographs.

What the Filter Blocks

The filter completely blocks emission lines from artificial light sources - mercury (Hg) and sodium (Na) discharge lamps - as well as airglow (natural atmospheric emission). It transmits only a narrow band centred on 656 nm, the hydrogen H-alpha emission line. The result is a dramatic increase in contrast between hydrogen HII regions and the sky. Blocking extends across the full spectrum from ultraviolet to infrared, so there is no loss of sharpness and no halo effects caused by IR transmission.

Hubble Palette Imaging

Astrophotography of emission nebulae is one of the most popular disciplines in modern amateur astronomy. The Astronomik H-alpha CCD 12nm filter combines with the Astronomik OIII CCD and SII CCD filters to produce three-colour narrowband images of emission nebulae in the so-called Hubble palette. This is possible even from locations with severe light pollution, and the results closely resemble the famous images from the Hubble Space Telescope.

It is important to note that Astronomik H-alpha filters are not suitable for solar observation. Using them to observe the Sun is dangerous, and the manufacturer explicitly advises against it.

Key Features

• Near 100% transmission at 656 nm (H-alpha emission line)
• 12nm bandpass - optimal for both city and dark-sky sites
• Compatible with fast optics from f/2.8 to f/15
• Completely blocks Hg and Na light pollution lines
• Blocks UV and IR across the full spectrum - no halos, no loss of sharpness
• Homofocal with all other Astronomik filters - no refocusing needed when switching filters during a session
• Optically polished substrate glass for sharp, high-contrast images without artefacts
• Suitable for cooled CCD cameras, CMOS sensors, and DSLR cameras
• Compatible with Astronomik OIII CCD and SII CCD filters for Hubble palette imaging
• Not suitable for visual observation or solar observation

Who Is This Filter For?

The Astronomik H-alpha CCD 12nm filter is an excellent choice for both beginners in narrowband astrophotography and experienced imagers. Its high transmission, robust build, and full compatibility with the Astronomik filter range make it a reliable companion for any emission nebula imaging session. Whether you image from a city balcony or a rural dark-sky site, this filter gives you the contrast you need to capture stunning results.

Technical Specifications