ZWO OIII 7nm 2" Filter - OIII7nmD2
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The OIII 7nm 2" filter from ZWO is a designed specifically for nebula observation. By allowing 7nm bandwidth of light through a wavenlength of 500nm, the OIII will block out all other light other than that which corresponds with the OIII emission lines. Using this filter goes beyond RGB filter use, as it will allow you to capture the beauty of many different nebulas, even in light polluted skies! The glass is also fine-optically polished to ensure accurate 1/4 wavefront.
OIII 7nm Filter Specifications
- Filter Size: 2"
- Mechanical Thickness: 7.5mm (5mm + 2.5mm thread)
- Thread: M48.5x0.75 male thread
- FWHM: 7±0.5nm
- Transmission Rate: About 90% transmission
- Infrared wavelength cut-off: 700-1100nm
- Transmission of off-band: <0.1%, OD3 (Optical Density)
While narrowband filters do not eliminate the effects of light pollution or increase a celestial object's brightness, it does reduce the transmission of light wavelengths products from artificial lights and sky glow: mercury vapor, both high and low pressure sodium vapor lights, and neutral oxygen emission in our atmosphere.