CCD sensors are sensitive over a very large region of the spectrum, deep into the infrared. This is particularly noticeable with exposures using short-focus and fast refractors. A barely seen, very noisy and indistinct double image behind the actual image can spoil a really good image.

The transmission of the blocking filter is optimized so that only the unwanted IR range is filtered out.

The filter has a 1.25" filter thread and can be simply screwed into the camera adapter or into an eyepiece.