The Optolong H-Alpha 7nm is a very narrow emission-line filter that works by permitting a 7nm bandwidth of light, focused on the 656nm wavelength through, and blocking the transmission of contrast-killing light pollution wavelengths. Wavelengths that are in charge of natural light pollution, or skyglow, are radically decreased, as is artificial light pollution brought about by high and low pressure sodium and mercury vapor lights. The outcome is a high contrast image that uncovers the H-alpha line in all its brilliance.
This Optolong H-Alpha EOS APS Clip filter will give a well defined contrast between the skyglow background and H-alpha transmitting objects, but since it has a FWHM of only 7nm, you won't see the same number of stars in the last picture as you would with the Optolong 12nm H-Alpha Filter.
The Optolong EOS APS H-Alpha 7nm Filter is made with Schott glass that has been multi-coated with ion-assisted deposition technology to guarantee scratch resistance and soundness on the central wavelength, or CWL. The filter cell is made of lightweight, strong metal and is CNC machined, sand-blasted, black anodized, and finally laser engraved.
Not Compatible with EF-S lenses