Optolong Oxygen OIII 6.5nm 1.25" Filter

Optolong filters are here to help all of us Earth based Astronauts.  As light pollution gets worse and worse we need something in our tool kit to help us  photograph the night sky.  Urban sprawl has created skies that just aren't conducive to imaging.  You can fight back with the assistance of filters. Some of you will have cameras that require separate filters that you can use in a drawer or filter wheel.  This particular Optolong Oxygen III filter is mounted in an ultra-thin cnc machined 1.25" threaded body.

The improved Narrowband OIII 6.5nm filter allows a 6.5nm bandwidth of light centered on a wavelength of 500nm through, which corresponds to OIII emission lines, and reducing the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor.  It also deals with both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).

OIII emits 495.9nm and 500.7nm and it is a blue-green colored filter. Many of images of planetary nebula and supernova remnants are taken only with H-alpha and OIII filters. They show great structural details, but have natural colors, looking like an RGB image.  As is customary for all Optolong filters that are designed for imaging, this filter blocks infrared wavelengths from 700nm to 1100nm so there is no need for a stand alone IR-Cut filter.

The filter itself is very well made.  The multi-layer anit-reflection coating is based on an Ion-assisted technology known for durability and Resistance to scratching.  The technology also provides stability to the CWL (central wavelength) allowing no deviation with temperature change.  The 1/4 wavelength Schott glass filter is housed in a very thin CNC machined housing..  The filter comes in a plastic case to protect your investment when not in use.

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