ALTAIR SII+ OIII- 1.25" dual band 6nm certified CMOS filter

Altair's ULTRA SII/OIII dual band narrow band filter with 6nm FWHM bandpass tuned. Available in 1.25" or 2" sizes ( the latter you can search for the article ALTAIR SII OIII- 2" Dual Band 6nm Certified CMOS Filter )

An individual spectrographic test report is included with each filter: another first from Altair.

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

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

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

In a process initiated by Altair, each individual filter in our certified range has an individual spectrographic test report with an actual resolution of 0.1 nm, unique to that particular filter. This is not a simulation or the overly optimistic advertising that often appears with foreign filters, such as those that are advertised as having 5 nm FWHM resolution but actually have 6-7 nm FWHM resolution and have generic test reports.

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

Below is an overview of the wavelengths transmitted by the DualBand filters:

Altair DualBand 6 nm Altair filter features:

• Capture the two main bands of emission nebulae at the same time, while suppressing light pollution, moonlight and airglow.
• Get more data in less time, opening up your imaging window, even in the summer months when it's not quite dark.
• If you have the 6 nm SII OIII Ultra filter and the Ha OIII version, you can capture twice as much OIII data in each imaging session and combine them for true Hubble SHO-style imaging with a color camera.
• An extremely steep bandpass produces maximum contrast in extreme light pollution conditions: 6 nm FHWM centered on the Oiii wavelength of 500.7 nm and 5.5 nm FHWM centered on the Sii wavelength of 671.6 nm.
• Halo suppression . We have received no reports of halos caused by this filter during testing.
• Can be used with astronomical mono or CMOS One Shot Color (OSC) cameras to obtain luminance data.
• It includes UVIR blocking for modified and unmodified DSLR cameras, plus an anti-reflective coating for maximum contrast.
• Best performance is obtained at focal ratios of F4.8 or lower, although it can be used at speeds as high as F3.6, with minimal impact on contrast (conservative estimate: faster speed is possible). As with any dichroic filter, contrast increases as the focal ratio number increases. More information on filter performance against light pollution and focal ratio here.
• Available in standard 1.25" or 2" astronomical filter sizes. Filters have standard Astronomy compatible filter threads and fit inside Altair magnetic filter holders (with appropriate slider) and standard astronomy filter wheels. Choose the 2" version for use with Altair's Canon / Nikon DSLR to Astro CMOS lens adapters. For Hypercam 183C and 533C or 533M, 585C and smaller sensors, choose the 1.25" filter. For larger sensors, choose the 2" version.

Altair's 6 nm dual band ULTRA filter specifications:

• *1st band, OIII CWL 500.7 nm FWHM 6 nm ~0.5 nm tolerance, T% 93 % 0.5 % tolerance.
• *2nd band, SII CWL 671.6 nm FWHM 5.5 nm ~0.5 nm tolerance, T% 93 % 0.5 % tolerance.
• OD5 blocking (0.001 %) on unwanted visual wavelengths
• 1.85 mm thick optical glass with 30 arc second parallelism. Parfocal with other Altair filters.
• Si02 "hard" top coat with UVIR blocking and anti-reflective coating for durability.