Optolong SII 6.5nm 2" 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 SII 6.5nm filter is mounted in an ultra-thin cnc machined 2" threaded body.

The Optolong SII filter allows a 6.5nm bandwidth of light centered on a wavelength of 672nm through, and reduces 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).  The SII filter is a great choice to use for astrophotography as it will help with contrast and reveal very subtle nebula details.

When used in conjunction with the  OIII-CCD and H-Alpha, such as the famous “Pillars of Creation” (M16 Eagle Nebula), you can start to bring your own "Hubble look" images from  your backyard.  That particular combination of the three filters for imaging, SHO set (H-alpha, OIII-CCD and SII-CCD), can be very helpful when the moon up, or in heavy light pollution, so your equipment is getting used rather than gathering dust. Remember, narrowband filters do not eliminate the effects of light pollution or increase the object’s brightness. In many cases, they increase the contrast between nebula and night sky, not brightening the nebula.

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.