Ha Oiii DualBand ULTRA 4nm CERTIFIED CMOS Filter 2"

The Altair Dual-Band ULTRA Ha Oiii nebula filter comes with a high resolution spectrographic test report.

Designed for imaging in extreme light pollution, E.g. in a major city, with a colour CMOS camera. 

This filter transmits only the H and Oiii light from emission nebulae, with almost total suppression of unwanted light, with OD6 (0.0001%) over the majority of unwanted visual wavelengths* for ultimate contrast. 

In a process pioneered by Altair, 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.

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 light pollution suppression.

Altair DualBand 4nm Filter Product 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.
• Extremely steep bandpass yields maximum contrast in extreme light pollution: 4nm FHWM centred on 500.7nm Oiii wavelength, and 4nm FHWM centred on the 656.3nm Ha wavelength.
• Halo suppression anti-reflective coating.
• 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.
• Best performance at focal ratios as fast as F4.0, optimised at F4.8 or slower, with contrast increasing as focal ratio increases. Faster than F3.5 requires an Altair Pre-Shifted filter 
• The 2" filter has standard M48x0.75mm thread, and fits inside the Altair Magnetic Filter holders, plus the Altair Canon / Nikon DSLR lens to astro CMOS adaptors. 

Altair 4nm Ha Oiii DualBand ULTRA Filter Technical Specifications:

• 1st band, Oiii CWL500.7nm FWHM 4nm tolerance ~0.5nm, T% 88%~91%
• 2nd band, Ha CWL 656.3nm FWHM 4nm tolerance ~0.5nm T% 90%~94%
• OD6 (0.0001%) from 200-760nm (visual wavelengths), and OD4.5 (0.003%) average from 800-1100nm (IR wavelengths) for the ultimate contrast. *Based on a test of 10 random samples in  batch 09-2023.
• 1.85mm thick optical glass with 30 arc sec parallelism.
• Si02 "hard" overcoat with UVIR Block and Anti-Reflection Coating for durability.