Altair Sii Oiii DualBand ULTRA 4nm CERTIFIED CMOS Filter 2" w test report

Here is a great review of this product! Thank you to Cuiv, The Lazy Geek

Altair Dual-Band ULTRA Oiii / Sii narrowband filter with extremely tight 4nm FWHM Bandpass.

This filter is designed to be the perfect complement to the Altair 4nm Ha Oiii filter. By using both filters you get twice the Oiii data you would otherwise - so you can now do proper Hubble pallette style imaging with a colour camera!

This filter delivers what most consider to be the perfect balance of flexibility and transmission. What's more it delivers 90% transmission over both wavelengths in the same filter, due to a special coating process.

For imaging in moonlight and extreme light pollution as in a major city, with a colour CMOS camera - or even in dark conditions if you want total control over your channels.

The filter transmits only the Sii 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.

In a process pioneered by Altair, each individual filter has an individual test report, unique to that particular filter, not a blanket test report for the whole batch.

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 DualBand 4nm Filter Features:

• Capture the two main emission nebulae bands at the same time, whilst suppressing light pollution, moonlight, and airglow.
• More data in less time, opening up your imaging window, even into the summer months when it isn't quite dark yet. Capture twice the Oiii data, whilst obtaining Sii to complement the Altair Ha Oiii DualBand filter.
• Extremely steep bandpass yields maximum contrast in extreme light pollution: 4nm FHWM centred on 500.7nm Oiii wavelength, and 4nm FHWM centred on the 671.6nm Sii wavelength.
• Halo suppression. We have not had any reports of halos caused by this filter in testing.
• 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 halo suppression. To see the AR coating in action, please see images demonstrating the same filter with and without the AR coating on the bright star, Capella in exactly the same conditions with the same settings.
• Best performance at focal ratios as fast as F4.8, with contrast increasing as focal ratio 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 4nm DualBand ULTRA Filter Specifications:

• 1st band, Oiii CWL500.7nm FWHM 4nm tolerance ~0.5nm, T% 90% ~3% Tol.
• 2nd band, Sii CWL 671.6nm FWHM 4nm tolerance ~0.5nm T% 90% ~4% Tol.
• OD4/5 Blocking (0.01%~0.001%) over the majority of unwanted wavelengths
• 1.85mm thick optical glass with 30 arc sec parallelism.
• Si02 "hard" overcoat with UVIR Block and Anti-Reflection Coating for durability.

Q: How to 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 LED light is also significantly reduced.
 
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 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).

Sensitive OSC or "One Shot Colour" CMOS cameras like the Altair Hypercam capture these wavelengths very efficiently, and allow them through the Bayer matrix. The filters also work with DSLRs (APS-C sensor size modified cameras are best, but normal ones will also work). When you have the complete stack of exposures, processing is relatively easy because of the large separation in colour. You can also use these filters as a "super luminance filter" for imaging nebulae with Mono cameras.

PLEASE NOTE: Demand for this product is very high and they are made in small batches. We sometimes temporarily suspend order to allow production to catch up. When we catch up with backorders we will re-enable ordering. We apologise for any inconvenience. Altair and Dealers reserve the right to change product specification and price without notice.