Astronomik H-alpha 12nm CCD MaxFR 1,25'' (M28,5)

MaxFR Astronomik photographic narrowband-emissionline filters for fast optical systems.

There is an ever-growing demand for filters suitable for extremely fast optical systems, like Celestron's RASA and Takahashi's Epsilon Astrographs.

Our new MaxFR emission line filters are perfectly suited to fast focal ratios. The Astronomik MaxFR series of narrowband-emission line filters meets the needs of deep-sky imaging with fast systems. For oxygen (OIII), hydrogen (H-alpha), and sulfur (SII) emission lines, you can choose filters with 12nm or 6nm bandwidths (FWHM).

Highest Transmission and Performance

The Astronomik MaxFR filters are designed for optimal performance with fast optical systems. With the renowned MFR Coating technique, these filters offer the best out-of-band blocking, covering the full range of wavelengths from UV to IR. These filters deliver extremely high contrast, minimized stray light, no halos, and needle-sharp stars.

• 12nm MaxFR filters: Usable from f/1.7 to f/8, achieving about 85% maximum transmission at f/1.4.
• 6nm MaxFR filters: Usable from f/2.2 to f/8, achieving about 90% maximum transmission at f/2.

For maximum contrast, the SII filter effectively blocks H-alpha and NII (nitrogen) light.

Imaging with Narrowband Emission Line Filters

Imaging with narrowband-emission line filters is ideal when observing from light-polluted sites. Narrowband H-alpha filters enable deep, contrast-rich imaging even under heavy light pollution or with the full moon in the sky. The H-alpha filter is best for red-glowing nebulae, while the OIII filter captures greenish/blueish structures like planetary nebulae and star-forming regions. The SII filter completes your HSO set for processing images like those from the Hubble Space Telescope!

Quality Aspects of Astronomik MaxFR Narrowband Emission Line Filters

• MFR Coating: Usable down to f/1.4 with 12nm filters and down to f/2 with 6nm filters.
• High-quality substrate: Made with stress- and striae-free, optically polished glass.
• Parfocal filters: All Astronomik filters are parfocal with very small thickness tolerance, ensuring no shift in focal plane when changing filters.
• Durability: Highly scratch-resistant, moisture-insensitive, and resistant to aging. Filters maintain full performance and meet specifications even after years of use.
• Integrated Blocking: Unwanted light is blocked across the entire spectral range from UV to IR.
• Wide range of sizes: Available in sizes from 1.25" to square 50mm x 50mm filters.
• Delivered in a high-quality protection and storage box.
• Backed by a 10-year guarantee.

Astronomik filters provide the highest possible quality for perfect images. The filters are a long-term investment, designed to work the same even after years of use. The new MFR coating ensures compatibility with nearly all instruments, extending the possibilities of astrophotography and deep-sky imaging.

Common Questions About Narrowband Emission Line Filters

• Which full-width half-maximum (FWHM) is best, 12nm or 6nm?

There's no definitive "best" choice between 12nm and 6nm filters. If you use a camera with extremely low dark current and effective cooling, the 6nm filters provide better contrast and star reduction. For DSLRs and dark-current-limited cameras, 12nm filters are ideal. If you're observing from heavily light-polluted sites or need maximum contrast, the 6nm filter offers significant benefits.

How Much Does Exposure Time Increase?

Exposure times don't necessarily increase, but you can expose for longer if needed. Narrowband filters block unwanted light, allowing you to capture deep-sky details even from light-polluted areas. While a 30-second exposure without a filter might saturate the sky background, the same exposure with a narrowband filter will yield a clean, black background, enabling longer exposures to capture faint structures.

Filter Selection

Select the appropriate filter size and FWHM to get a list of available options that suit your setup.