ALTAIR ULTRA 4nm dual band HA OIII 2" CMOS filter

The Altair Dual-Band ULTRA Ha OIII Altair Haze Filter comes with a high resolution spectrographic test report.

Designed for imaging in extreme light pollution conditions, e.g., in a large city, with a color CMOS camera.

This filter transmits only H and OIII light from emission nebulae, with near-total suppression of unwanted light, with OD6 (0.0001 %) over most unwanted visual wavelengths* for maximum contrast.

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.

Narrow-band bicolor image capture is a booming new trend in astrophotography, especially popular in areas with light pollution or intense moonlight. First, Altair introduced you to the TriBand and Quad Band filters, now we have the DualBand Ultra for the most extreme suppression of light pollution

Altair DualBand 4 nm filter product features:

• Capture the two main bands of emission nebulae at the same time, while suppressing light pollution, moonlight and airglow.
• More data in less time, extending your imaging window even in the summer months when it is not yet fully dark.
• An extremely steep bandpass produces maximum contrast in extreme light pollution conditions: 4 nm FHWM centered on the Oiii wavelength of 500.7 nm and 4 nm FHWM centered on the Ha wavelength of 656.3 nm.
• Suppression of halos. We have received no reports of halos caused by this filter during testing.
• Can be used with mono or CMOS One Shot Color (OSC) astronomical cameras to obtain luminance data.
• It includes UV blocking for modified and unmodified DSLR cameras, plus an anti-reflection coating for halo suppression. To see the anti-reflective coating in action, see images showing the same filter with and without the anti-reflective coating on the Capella shining star in exactly the same conditions at the same settings.
• Best performance at focal ratios as fast as F4.0, optimized to F4.8 or slower, with contrast increasing as the focal ratio increases. For speeds above F3.5, an Altair Pre-Shifted filter is required (contact us for more information). More information on filter performance against light pollution and focal ratio here.
• The 2" filter has a standard M48x0.75mm thread and fits inside Altair magnetic filter holders as well as Altair's Canon / Nikon DSLR to astro CMOS lens adapters.

Technical specifications of the Altair 4nm Ha OIII DualBand ULTRA filter:

• 1.1st band, OIII CWL500.7 nm FWHM 4 nm tolerance ~0.5 nm, T% 88 % ~ 91 %
• 2.1st band, Ha CWL 656.3 nm FWHM 4 nm tolerance ~0.5 nm T% 90%~94% OD6 (0.0001 % ~ 91 %)
• OD6 (0.0001 %) from 200 to 760 nm (visual wavelengths) and OD4.5 (0.003 %) averaged from 800 to 1100 nm (IR wavelengths) for maximum contrast. *Based on a test of 10 random samples from lot 09-2023.
• Optical glass 1.85 mm thick with 30 arc second parallelism.
• Si02 "hard" top coat with UVIR blocking and anti-reflective coating for durability.