The Baader Planetarium DSLR-Astro Conversion Filter for Canon EOS cameras turns your Canon DSLR into a superb deep sky AstroCamera. Baader Planetarium DSLR conversion filter replaces the factory correcting filter ("hot mirror"). The special substrate is coated with Baader's renowned coatings. Imagers can now gain full efficiency at H-Alpha wavelengths and at full resolution. The thickness of the Baader DSLR filter has been designed to maintain the correct factory focal point. This filter is intended for amateurs that are comfortable replacing their camera's stock filter.