This combo consists of two Altair Dual-Band ULTRA DualBand filters with a tight 6nm FWHM Bandpass.

Individual spectrographic test report included with each filter - another Altair first.
Available in 1.25" or 2" standard astronomy filter sizes, please choose size when ordering.

You get two filters in the Combo:
DualBand 6nm Ha Oiii Filter - Code F125DB6NM-Ha-OIII for 1.25"
DualBand 6nm Sii Oiii Filter - Code F125DB6NM-SII-OIII for 1.25"

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.

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 the Ha and Sii wavelengths are 5.5nm with 93% transmission. Tolerances are FWHM 0.5nm and T0.5% respectively.

In a process pioneered by Altair Astro, 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. Rest assured you are not playing "Chinese filter roulette".

The DualBand filters transmit only the main wavelengths from emission nebulae, with almost total suppression of unwanted light, giving OD5 (0.001%) bocking over the majority of unwanted visual wavelengths for excellent contrast. 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 6nm ULTRA Filter Features:

• Capture two main emission nebulae bands at the same time, per filter, 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 Sii Oiii Ultra filter and the Ha Oiii filter combo, 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, 5.5nm FHWM centred on the Sii and Ha wavelengths.
• 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.
• Available in 1.25" or 2" standard astronomy filter sizes. The filters have standard Astronomy compatible filter threads, and fit inside the Altair Magnetic Filter holders (with appropriate slider), and standard astronomy filter wheels. Choose the 2" version for use with the Altair Canon / Nikon DSLR lens to astro CMOS adaptors. For Hypercam 183C and 533C or 533M, 585C and smaller sensors choose the 1.25" filter. For larger sensors choose the 2" version.

Scope of Delivery:

• Filterset SII, OIII, Ha 1.25"