The Astronomik oiii filter is ideal for photographing nebulae with oxygen emissions from both light-polluted and dark observation areas.
The Astronomik oiii filter significantly increases the contrast between objects emitting light at 496 nm and 501 nm (OIII lines) and the sky background, thus enabling long exposure times for deep and high-contrast images.
The filter blocks the emission lines of high- and low-pressure sodium (Na) and mercury (Hg) vapour lamps, the maxima of typical LED lights, all lines of the natural airglow, and almost all of the interfering moonlight.
The Astronomik oiii filter effectively blocks all unwanted light at wavelengths other than 496 nm and 501 nm, from ultraviolet (UV) to infrared (IR).
The Astronomik MaxFR coating
Both the Astronomik MFR and MaxFR coatings offer extremely high contrast, minimal stray light, no halos and razor-sharp stars. Furthermore, they provide the best possible blocking across the entire spectral range from UV to IR.
The MaxFR coating ensures that Astronomik narrow-band emission line filters can be used with extremely fast optical systems such as the Celestron RASA and the Takahashi Epsilon Astrograph. Unlike filters from other manufacturers, which often offer special “high-speed” versions, Astronomik’s MaxFR filters retain their transmission characteristics even in standard optical systems that are less light-sensitive. Using a MaxFR filter with a standard optical system has no disadvantages whatsoever and saves you a lot of money on multiple filter sets.
Difference between Astronomik 12nm, 6nm and 4nm Filters
The choice between 12nm, 6nm and 4nm half-width depends on your imaging conditions and camera type. There is no universally ‘best’ option – each half-width serves a specific purpose.
The 6nm Astronomik narrow-band emission line filters are usually the best choice for astrophotography. They are ideal for imaging faint objects in star-rich regions of the Milky Way, as they typically halve the number of stars in the image compared to 12nm filters, thereby significantly simplifying image processing.
The 6nm narrow-band emission line filters are particularly the first choice if you are using a CMOS astro camera or a modern system camera with very low dark current, or if you are conducting observations from a location with heavy light pollution. Thanks to their excellent suppression of the sky background, you can use long exposure times. The 6nm filters ensure a dark background and excellent rendering of details in faint nebulae.
