Caveat to what was written in the previous post: the OSC camera sensor needs to be sensitive to the Ha wavelengths. Your normal, everyday DSLR is _not_ sensitive to this light. That's why you get them Ha-modified or astro-modified. Dedicated astrophotography cameras do not need such modifications because no filter was put in front of the sensor in the first place.
Filters like the Optolong L-eXtreme take advantage of the OSC sensor by only allowing certain wavelengths of light to pass. In the L-eXtreme's case, the light allowed to pass are the Ha and O3 wavelengths (Ha maps to the R channel and O3 maps to both the G and B channels). Because they only allow a very narrow band of light to pass, they are only good for objects that emit that type of light: nebulae. The filter is a terrible choice fo shooting galaxies or other broadband emitters. You can, however, use it to supplement data taken without the filter. In other words, if you target, say M101, you might take 8 hours of RGB data using your OSC (no filters) and then maybe take 4 hours of data using your OSC with the L-eXtreme (and use the R channel as Ha to enhance the first data).