ZWO H Alpha 7nm 2" Filter - HA7nmD2
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Narrowband filters are great if you are looking to reduce transmissions of certain types of light like mercury vapor, both low and high pressure sodium vapor (these three coming from artificial light), and neutral oxygen emission in the atmosphere (skyglow). While Narrowband filters do not eliminate the effects of light pollution or increase the celestial object's brightness, they can increase the contrast between the object and the night sky.
ZWO H-alpha 7nm filter is a 2" filter with a M48x0.75 male thread. The bandpass of the filter is 7nm, and it passes light at 656nm wavelength. If you want high contrast astroimaging, then this Hα filter will deliver an excellent performance. The light transmission rate for the filter comes up to 80% and the glass has been fine-optically polished to ensure accurate 1/4 wavefront. So, even in areas of strong light pollution, you can still explore the night sky with your imaging equipment!
Hα Filter Specifications
- Mechanical Thickness: 7.5mm (5mm + 2.5mm thread)
- FWHM: 7±0.5nm
- Infrared wavelength cut-off: 700-1100nm
- Transmission of Off-band: <0.1%