Dual-band filter for two spectral lines:
SII filter: The narrowband S-II 7nm filter passes light at 672nm wavelength with a bandpass of 3nm which is designed for nebula fotography.
It is suitable for most emission nebulae, planetary nebulae and supernova remnants.
f you want the look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” (the Eagle Nebula, Messier 16), then the next filter to consider adding to your collection after H-a and OIII is the SII (es-two) or sulfur filter. The SII filter, like H-a, is a deep red filter near 672 nm. H-a, OIII and SII filters provide that Hubble look for many emission nebula. Again, tri-color narrowband imaging with these three filters can be done with the moon up, so your equipment is not sitting dormant for several weeks.
OIII Filter: The narrowband O-III 3nm filter is designed for nebula observation allowing 3nm bandwidth of light centered on a wavelength of 500nm through, which corresponds to OIII emission lines, blocking out all other light.
This filter offers what most consider to be the perfect balance between flexibility and transmission. Thanks to a special coating process, the filter also achieves 90% transmission for both wavelengths.
For shooting in moonlight and extreme light pollution, such as in a large city, with a colour CMOS camera – or even in darkness, when you want full control over your channels.
The filter only allows [S II] and [O III] light from emission nebulae to pass through, while almost completely suppressing unwanted light, with an OD4/5 (0.01%~0.001%) for most unwanted visual wavelengths.
In a process developed by Altair, an individual test report is created for each individual filter, which applies only to that filter and not to the entire batch.
Narrowband bi-colour imaging is a growing new trend in astrophotography, particularly popular in light-polluted areas or in bright moonlight. Altair first launched the TriBand and Quad Band filters, and now offers the DualBand Ultra for the most extreme signal-to-background performance.
Coating: HardSiO2 coating with UVIR block and anti-reflective coating for long durability.
