The Altair 3.5 nm dual-band ULTRA [S II]/[O III] nebula filter comes with an individual, high-resolution spectrographic test report.
Altair dual-band filters enable you to take images in bright moonlight and under conditions of extreme light pollution, such as those found in major city centres like London or Tokyo, using a colour CMOS camera – or even in complete darkness, should you wish to have full control over your channels.
This filter transmits only the [S II] and [O III] light from emission nebulae and suppresses unwanted light almost completely, achieving an optical density (OD) of 6 or better (~0.0001 per cent) across the majority of unwanted visible wavelengths.
Using a process developed by Altair, each individual filter comes with its own test report specific to that filter – rather than, as with other manufacturers, a general test report covering the entire batch. Please note that these are precise measurements taken with a professional spectrograph at a resolution of 0.1 nm.
Narrow-band dual-colour imaging is an emerging trend in astrophotography, particularly popular in areas affected by light pollution or under bright moonlight. Altair was the first to launch the TriBand and QuadBand filters; now the DualBand Ultra is available, offering an optimal signal-to-background noise ratio.
