Filters from the MaxFR series are optimized for astrophotography with very fast telescopes, such as Celestron RASA optics or theOmegon Per astrograph.
For the three most important lines, namely OIII, H-alpha, and SII, the series provides filter sets with a half maximum width of 12nm and 6nm.
The filters get the best possible out-of-band blocking over the entire spectral range from UV to IR! The advantages are maximum contrast, minimal stray light, no halos and the finest star imaging. With the Astronomik MaxFR narrow-band line filters, you get raw data of the highest quality: The optimal starting point for further processing into an impressive astrophoto!
Maximum transmission of the filters is required for the best possible yield:
- For MaxFR filters with a FWHM of 12nm, this means unrestricted usability from f/1.7 to f/8 and around 85% of the maximum transmission
- For MaxFR filters with a FWHM of 6nm, this means unrestricted usability from f/2.2 to f/8 and around 90% of the maximum transmission
For particularly high-contrast results, the SII filter is optimized to prevent the passage of H-alpha and NII (nitrogen).
Photography with narrow-band line filters: If you are observing under bright skies, starting with astrophotography with line filters is the best way to create successful images. As a rule, an H-alpha filter is the first sensible purchase: With this filter, you can easily create detailed recordings even with a full moon or a very bright sky! It is also the right filter for all nebulae that shine in red light.
The OIII filter expands your options enormously, because it allows all greenish/bluish structures to be displayed in detail and with high contrast. Especially planetary nebulae and star-forming regions are rewarding targets! With the SII filter, your HSO filter set is complete and you can use the three channels to create color images like the Hubble Space Telescope!
The H-beta filter is not available in the 6nm version, as this filter has almost no useful application.
Which FWHM is the right one? When shooting under dark skies, when using a DSLR and even many cooled CCD cameras, the images are limited by the camera's dark current and not by the background brightness of the sky. Here, further suppression of the sky background through a lower FWHM does not reveal more details in the object! Compared to the 6nm filters, the 12nm filters have the advantage that it is usually easier to find tracking stars on cameras with a built-in tracking sensor!
If you own a camera with a particularly low dark current and good cooling, the 6nm filter will play out all its advantages: An even stronger suppression of the brightening of the sky enables even longer exposure times and thus even deeper images! Due to the low FWHM, the stars become tiny, faint stars almost completely disappear. -Especially in regions of the Milky Way with many stars, the 6nm filters also enable weak objects to be displayed in high contrast without them getting lost in the swarm of stars.
In short, the use of 12nm filters is recommended for DSLR and all dark current limited cameras.
The 6nm filters are the right choice in places with heavy light pollution, for cameras with extremely low dark current, and when weak objects require the highest contrast in the image!
