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IDAS HEUIB-II H-Alpha Enhanced UV/IR Cut Filter
The IDAS HEUIB-II is a UV/IR-cut filter designed to enhance the 656.3nm H-alpha wavelength for imagers using one-shot color cameras. By suppressing the red end of the spectrum beyond H-alpha, it enhances H-alpha nebulae and brings the reddish color balance of a UV/IR-modified camera closer to normal.
A UV/IR Cut Filter Tuned for 656.3nm H-alpha Emission
Regular astronomical IR-cut filters, such as the IDAS UIBAR-III, let some red-end light through. The HEUIB-II widens the red suppression range, even compared with the earlier IDAS HEUIB, so the H-alpha region at 656.3nm is enhanced in the image.
For imagers with modified DSLRs or mirrorless cameras, this filter serves a dual purpose. It brings the reddish color balance of a UV/IR-modified camera closer to normal. It gives a good white balance even with the camera's auto white balance setting. The filter's design utilizes Ion-Gun Assist Deposition (IGAD) coating technology, which densifies the multi-layer coating: the layers are as hard as quartz glass and show almost no aging from temperature and humidity changes in normal living environments.
Managing Incidence Angles Down to 17 Degrees
As an interference filter, the HEUIB-II's performance is dependent on the angle at which light passes through it. To avoid color shifts and maintain its specified bandpass, the angle of incidence must be controlled. When placing the filter in front of a camera lens, IDAS recommends using lenses with a field angle of 34 degrees or less, so the light rays strike the filter at an angle no greater than 17 degrees.
For drop-in filter systems placed between the lens and sensor, the requirements are more flexible. With an APS-C sensor and a lens with a back focal distance of 40mm or more, you can use optics as fast as f/2 while keeping the maximum incidence angle below 20 degrees.
7 Formats for Systems from RASA 8 to ZWO Cameras
The HEUIB-II comes in seven formats. Drop-in adapters and filter drawers are sold separately.
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2" (M48) & M52: Threaded M48x0.75 (2") and M52x0.75 cells with a 2.0mm substrate.
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DS Drop-in: A 1.1mm substrate filter designed for the IDAS AD42-DS drop-in mount adapter system.
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Di2 Drop-in: A 2.0mm substrate filter made specifically for the IDAS AD19.4 adapter, commonly used with the Celestron RASA 8.
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DRT Drop-in: A 2.0mm substrate filter in a frame compatible with the Canon EF-EOS R drop-in mount adapter and select Meike and Kolari adapters.
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DZ Drop-in: A framed 2.0mm substrate filter with a large 47mm effective aperture, designed for ZWO FD-M54-II and FD-M42-II filter drawers.
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ZF Drop-in: A 1.1mm substrate filter that drops into the T-ring of ZWO cameras with a 6.5mm flange back, also compatible with the IDAS AD19.4 adapter.
Cleaning and Care for 2.0mm and 1.1mm Substrates
Blow off gritty particles before you wipe the filter.
For loose dust, always start by using a clean air blower. If stains or fingerprints remain, use a new, soft lens cleaning paper impregnated with a neutral-pH lens cleaning fluid. Gently wipe the surface to remove residue. Never use acidic or alkaline cleaning solutions.
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Can I use the Di2 version of the IDAS HEUIB-II with my Celestron RASA 8?
Yes, the Di2 format is specifically designed for this purpose. It fits into the IDAS AD19.4 drop-in adapter, which is made for the RASA 8.
What is the practical difference between the IDAS HEUIB-II and a standard UV/IR cut filter?
A standard UV/IR cut filter is designed to block UV and IR light while passing the visible spectrum as evenly as possible. Regular astronomical IR-cut filters let some red-end light through. The HEUIB-II suppresses a wider red range, which enhances the 656.3nm H-alpha region and brings a modified camera's color balance closer to normal.
Which IDAS HEUIB-II filter do I need for a ZWO filter drawer like the FD-M54-II?
You need the DZ drop-in format. The IDAS DZ filters are designed as a direct replacement for the standard ZWO filter holders, allowing you to slide them into the FD-M54-II or FD-M42-II filter drawers. The DZ version offers a large 47mm clear aperture to minimize the risk of vignetting on full-frame sensors.
Why do my stars have a slight color shift at the edge of the frame with my 24mm camera lens?
This is caused by the angle of incidence. The HEUIB-II is an interference filter, and its spectral properties shift as the angle of incoming light becomes steeper. For filters mounted in front of a lens, IDAS recommends a maximum field angle of 34 degrees. A 24mm lens on a full-frame camera has a much wider field of view, causing a significant incidence angle at the corners and leading to color shifts.
Does the IDAS HEUIB-II replace a narrowband H-alpha filter?
No. The HEUIB-II is a UV/IR-cut filter that passes the visible spectrum and enhances the H-alpha region. A narrowband H-alpha filter passes only a narrow band around H-alpha and blocks the rest.
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| Brand |
IDAS (ICAS Enterprises, Japan) |
| Available Formats |
2" (M48) mounted = 2" (M48x0.75) threaded cell, 2.0mm substrate; M52 mounted = M52x0.75 threaded cell, 2.0mm substrate; DS drop-in (IDAS AD42-DS) = drop-in filter for the IDAS AD42-DS drop-in mount adapter, 1.1mm substrate; Di2 drop-in (IDAS AD19.4 / RASA 8) = drop-in filter for the IDAS AD19.4 drop-in adapter for RASA 8, 2.0mm substrate; DRT drop-in (Canon EF-EOS R) = drop-in frame for the Canon EF-EOS R drop-in mount adapter, Meike MK-EFTR-C (EF-R) and MK-EFTE-C (EF-E) adapters, and the Kolari EF-EOS R drop-in filter mount adapter, 2.0mm substrate; DZ drop-in (ZWO FD-M54-II) = drop-in frame for the ZWO FD-M54-II and FD-M42-II filter drawers and ZWO Canon EF / Nikon F adapters with a filter drawer, 47mm effective aperture, 2.0mm substrate; ZF (ZWO cameras) = drops into the T-ring of ZWO M42 male-mount cameras (6.5mm flange back), also fits the IDAS AD19.4 drop-in mount |
| Substrate Thickness |
2" (M48) mounted 2.0mm, M52 mounted 2.0mm, DS drop-in (IDAS AD42-DS) 1.1mm, Di2 drop-in (IDAS AD19.4 / RASA 8) 2.0mm, DRT drop-in (Canon EF-EOS R) 2.0mm, DZ drop-in (ZWO FD-M54-II) 2.0mm, ZF (ZWO cameras) 1.1mm |
| Coating Type |
Interference filter (spectral characteristics depend on the angle of incoming light) |
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IDAS HEUIB-II H-Alpha Enhanced UV/IR Cut Filter
× 1 (format chosen at checkout)
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Contact us for warranty details.
