How does the IDAS GNB filter perform on a galaxy like M33 with an IMX294 camera?
When using the IDAS GNB with a conventional sensor like the IMX294 on a galaxy like the Triangulum Galaxy (M33), the filter enhances the overall colorfulness of the galaxy. However, the strong near-infrared signal passed by the filter may slightly desaturate the distinct red and blue-green colors of the HII and OIII regions within the galaxy's spiral arms.
I have a ZWO camera with an FD-M54-II filter drawer. Which IDAS GNB format do I need?
The DZ format is made for this. It replaces the standard filter holders in ZWO FD-M54-II and FD-M42-II filter drawers. It offers a larger 47mm clear aperture compared to standard M48 filters, which helps reduce vignetting on full-frame sensors.
Why does my IDAS GNB filter produce halos around bright stars?
The halos are a known side effect of imaging in the near-infrared (NIR) spectrum. Most camera sensor windows have anti-reflection coatings optimized only for visible light. The GNB filter is designed to pass NIR light, which can cause internal reflections between the filter and the unoptimized camera glass, resulting in halos. This effect is more pronounced with conventional sensors (like the IMX294) than with NIR-enhanced sensors (like the IMX585).
What's the main difference between the IDAS GNB and a standard dual-band nebula filter?
A standard dual-band filter passes only specific visible wavelengths like H-alpha and OIII, blocking everything else. The IDAS GNB filter passes those same nebula lines but also passes a broad range of near-infrared (NIR) light. IDAS designed it this way so that galaxies can be imaged as well as nebulae, since the near-infrared region is hardly affected by artificial light pollution.
Do I need a special camera to use the IDAS GNB filter?
No, but results are optimized with certain sensors. IDAS recommends using the GNB filter with cameras that have enhanced near-infrared sensitivity, such as those with the Sony IMX585 or IMX464 sensors. It will still work with conventional color cameras (e.g., IMX294), but the NIR signal may alter the final color balance.
How should I clean my IDAS GNB filter?
Follow this procedure:
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For loose dust: Use a clean air blower to gently remove particles.
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For stubborn stains: After blowing off loose dust, use a lens cleaning paper wetted with a neutral (not acidic or alkaline) lens cleaning fluid. Wipe gently and slowly.
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Silicone-impregnated cloth: If using one, always blow dust off first, then wipe gently.
