High quality, fully multi-coated glass IR blocking filter
CCD cameras are very sensitive over the entire spectrum - in the infrared as well as in the visual. Many telescopes correct for chromatic aberration in the visual range but not in the infrared (which is invisible to us). This means that images may appear out of focus - especially if the telescope is not a purely reflecting design.
An IR blocking filter provides the best colour balance and greatest sharpness. This filter blocks infrared radiation while allowing over 94% of the entire visible light spectrum through, and so does not distort the colours.
The IR blocking filter can simply be screwed into the nosepiece of the camera.