Altair V2 coatings are very effective for LED light pollution, with a deeper blocking factor of OD>6 for wavelengths below 440nm, and OD5 for the visual range.

Based on an average sample of 90 filters tested, the Bandwidth at FHWM for Oiii is 6nm with 93% transmission, and the FWHM for Sii is 5.5nm with 93% transmission. Tolerances are 0.5nm and 0.5% respectively.

This is the filter for imaging in moonlight or light pollution with a colour CMOS camera - or even in dark-sky conditions if you want total isolation and control over your channels, narrowband-style.

In a process pioneered by Altair, each individual filter in our certified range has an individual spectrographic test report with 0.1nm true resolution, unique to that particular filter. This is not a simulation, nor the overly optimistic marketing you tend to get with foreign filters - such as those advertised at 5nm FWHM but which actually have 6-7nm FWHM, and which have generic test reports.

The DualBand Ha/Oiii filter transmits only the Sii and Oiii light from emission nebulae, with almost total suppression of unwanted light, with OD5 (0.001%) over the majority of unwanted visual wavelengths. Narrowband Bi-Colour imaging is a growing new trend in astrophotography, especially popular in light polluted areas, or bright moonlight. First, Altair brought you the TriBand and Quad Band filters, now we have the DualBand Ultra for the most extreme signal vs. background performance.

Altair 6nm DualBand ULTRA Filter Specifications:

• *1st band, Oiii CWL 500.7nm FWHM 6nm ~0.5nm tolerance , T% 93% 0.5% Tolerance.
• *2nd band, Sii CWL 671.6nm FWHM 5.5nm ~0.5nm tolerance, T% 93% 0.5% Tolerance.
• OD5 Blocking (0.001%) over unwanted visual wavelengths
• 1.85mm thick optical glass with 30 arc sec parallelism. Parfocal with other Altair filters.
• Si02 "hard" overcoat with UVIR Block and Anti-Reflection Coating for durability.

• Altair 1.25" Sii Oiii DualBand 6nm CERTIFIED CMOS Filter & test report