The Canon EOS 20Da is an 8.2-megapixel semi-professional DSLR camera designed specifically for astrophotography. It was initially announced on February 14, 2005 for release only in Japan. On June 1, 2005, Canon announced that the 20Da would be made available world-wide. It is a variant of the Canon EOS 20D. It accepts EF and EF-S lenses.
One of the changes made to the 20Da over the 20D is the replacement of the "hot mirror" IR filter which covers...
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The Canon EOS 20Da is an 8.2-megapixel semi-professional DSLR camera designed specifically for astrophotography. It was initially announced on February 14, 2005 for release only in Japan. On June 1, 2005, Canon announced that the 20Da would be made available world-wide. It is a variant of the Canon EOS 20D. It accepts EF and EF-S lenses.
One of the changes made to the 20Da over the 20D is the replacement of the "hot mirror" IR filter which covers the CMOS sensor on the 20D. In conventional photography, the IR filter is used to make the spectral response of the CMOS sensor more like that of the human eye. In this way, the pictures gathered by the sensor more closely resemble the world as we see it. In astrophotography, many objects of interest emit strongly in the so-called H-α line, which is heavily attenuated by the IR filter on the 20D. The IR filter of the 20Da passes 2.5 times as much light at around this 656 nm wavelength as does the filter of the 20D, allowing more fine detail...
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