The Astronomik MaxFR filter series was created for extreme compatibility with fast focal ratio telescopes such as those in the Celestron RASA series or Epsilon Astrographs from Takahashi. 

Available in both 6nm and 12nm versions, these filters have built-in MFG coating to provide the best possible blocking across the entire range of wavelengths from the UV up to IR. Thanks to this feature, these filters have incredibly high contrast, very little stray light, no halos, and, of course, perfectly sharp stars.

The 6nm MaxFR filters provide unlimited usability for focal ratios between f/1.8 and f/2.2 with roughly 90% transmission rates.

The 12nm MaxFR filters then perform best between focal ratios of 1.7 and 1.8 with at least 85% transmission rates while also being able to function at f/1.4.

Key Features of the Astronomik MaxFR Filter Series:

• MFR Coating for incredibly precise optical clarity.
• Made from a high-quality substrate in extremely thin layers.
• All Astronomik filters are parfocal so you can swap with freedom!
• Extremely scratch-resistant, not sensitive to moisture, and do not degrade with age.
• Effectively blocks light across the spectrum, leaving only the desired wavelengths.

• Perfect for fast focal length telescopes!
• Extremely scratch-resistant and parfocal with all Astronomik filters.
• Available in either 6nm or 12nm versions.
• This is the 12nm SII version.
  

• Astronomik SII 12nm CCD MaxFR Clip-Filter Nikon XL
• Plastic box