Altair Ha Oiii DualBand 6nm CERTIFIED CMOS Filter & test report

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.

Unlike other filters, Altair specifications are conservative. In a process pioneered by Altair, each individual filter in our certified range has an individual spectrographic test report, corresponding to a serial number unique to that particular filter - not a simulation, nor the overly optimistic marketing you tend to get with foreign filters. 

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:

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 to OSC Narrowband filters actually 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 LED light is also significantly reduced.

Q: How do I process subs with an Altair DualBand filter and colour CMOS camera? For more information on processing please check out this YouTube Altair TriBand V1 Filter processing video by Astrostace. (new window).

Q: What does "DualBand" mean?

There are 3 types of OSC line filters in the Altair range:

1. Dual-Band - the allowing only the thinnest peaks of two emission lines, for example Ha 656.3nm and 500.7nm Oiii light from emission nebulae through. (Recommended for extreme light pollution in the worst possible conditions).
2. Tri-Band - combines Ha into a red zone, and H-beta + Oiii into a green/blue zone. (For urban light pollution).
3. Quad Band - combines Sii AND Ha into a red zone, and H-beta + Oiii into a green/blue zone. (For suburban / moderate light pollution).

Overview of Multiband Filters:

Sensitive OSC or "One Shot Colour" CMOS cameras like the Altair Hypercam capture the above wavelengths very efficiently, and allow them through the Bayer matrix. The filters also work with DSLRs. When you have the complete stack of exposures, image processing is relatively easy in software, because of the discrete separation in colour channels. You can assign any colour to the any channel too for limitless creativity! Multiband filters can also be used as a "super luminance filter" for imaging nebulae with Mono cameras to enhance brightness of nebulae and suppress stars.

PLEASE NOTE: Demand for this product is high and they are made in small batches. We sometimes temporarily suspend ordering to allow production to catch up. When we catch up with backorders we will re-enable ordering. If the "backorder" option shows you can be assured of a place in the production queue. We apologize for any inconvenience. Altair and Dealers reserve the right to improve or change product specification and price without notice.

USA customers can also buy this filter from Land Sea and Sky in Texas.