Altair Dual-Band ULTRA Ha / Oii narrowband filter with a tight 6nm FWHM Bandpass.
Altair V2 coatings are very effective for LED light pollution, with a deeper blocking factor of OD>6 for wavelengths below 440nm, and OD4.5 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 Ha 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, unique to that particular filter. 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 do not have individual test reports.
The DualBand Ha/Oiii filter transmits only the Ha and Oiii light from emission nebulae, with almost total suppression of unwanted light, with OD4/5 (0.01%~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.
Here's an overview of wavelengths transmitted by DualBand filters:
| | DualBand Sii Oii | DualBand Ha Oiii (this filter) |
|
| Ha | No | Yes | |
| Sii | Yes | No | |
| Oiii | Yes | Yes | 2x the Oiii Data when used together! |
Altair DualBand 6nm Filter Features:
- Capture the two main emission nebulae bands at the same time, whilst suppressing light pollution, moonlight, and airglow.
- Acquire more data in less time, opening up your imaging window, even into the summer months when it isn't quite dark.
- If you have the 6nm Ha/Sii Ultra filter and the Sii/Ha version, you can capture twice the Oiii data in each imaging session and combine them for true SHO Hubble style imaging with a colour camera!
- Extremely steep bandpass yields maximum contrast in extreme light pollution: 6nm FHWM centred on 500.7nm Oiii wavelength, and 5.5nm FHWM centred on the 656.28nm Ha wavelength.
- No halos. We have not had any reports of halos caused by this filter in testing, and we don't expect any with our new V2 hard coating technology.
- Can be used with One Shot Colour (OSC) CMOS or mono astronomical cameras for luminance data.
- Includes UVIR blocking for both modified and un-modified DSLR cameras, plus an anti-reflection coating for the ultimate in contrast.
- Best performance at focal ratios at F4.8 or slower, however can be used as fast as F3.6, with minimal contrast impact (conservative estimate - faster may be possible). Like any dichroic filter, contrast increases as focal ratio number increases. More info about light pollution filter performance and focal ratio here.
- The 2" filter has standard M48x0.75mm thread, and fits inside the Altair Magnetic Filter holders, standard 2" filter wheels, plus the Altair Canon / Nikon DSLR lens to astro CMOS adaptors.
Altair 6nm DualBand ULTRA Filter Specifications:
- *1st band, Oiii CWL 500.7nm FWHM 6nm ~0.5nm tolerance , T% 93% 0.5% Tolerance.
- *2nd band, Ha CWL 656.28nm FWHM 5.5nm ~0.5nm tolerance, T% 93% 0.5% Tolerance.
- OD4/5 Blocking (0.01%~0.001%) over the majority of unwanted 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.
Q: How do OSC Narrowband filters work? Altair OSC narrowband filters work by isolating the primary nebulae emission zones in the red and blue wavelengths, and separating them into two main "zones" with a wide separation for easy capture with a colour camera - all in one exposure! Not only is capture more convenient with one filter, but processing is easy too, thanks to the wide separation of the green/blue and red "zones". Light pollution control is extremely effective and even LED light pollution is significantly reduced.
Q: What does "DualBand" mean? Here's an article explaining what a DualBand light pollution filter is.
Q: What cameras are compatible with DualBand light pollution filters? Sensitive OSC or "One Shot Colour" CMOS cameras like the Altair Hypercam capture light from emission nebulae very efficiently, and allow them through the Bayer matrix, and are mostly used with Dual Band filters. These filters also work with DSLRs or in fact any colour camera!
PLEASE NOTE: Demand for this product is very high. We sometimes temporarily suspend order to allow production to catch up. When we catch up with backorders we will re-enable ordering. We apologize for any inconvenience. Altair and Dealers reserve the right to change product specification and price without notice.
Scope of Delivery
Products specifications
| Filter thread / size | 2" |
| Cell | Aluminium |
| Thickness | 1.85mm |
| Type | Line Filter |
