This filter finds application in planetary imaging. The passband begins in the deep red region at 670nm and extends well into the infrared. This long wave light can be used in IR LRGB imaging to produce a sharper luminance image for the best planetary contrast.

Often the atmospheric seeing is much steadier at these IR wavelengths.

Images taken with IR as luminance channel have produced some of the finest Mars pictures during the last opposition. See the picture opposite which was taken with a webcam and IR-Pass filter. Contrast on Jupiter and other planets is also visibly enhanced.

Both surfaces are optically polished to produce diffraction limited images and professionally coated to very tight tolerances.

The Baader IR Pass filter blocks nearly the total visible spectrum. At 685 Nanometers (beyond the red part of the spectrum) 50% of light passes through the filter. Beyond that transmissioin is higher. In order to be able to find focus with your eyes the light transmission begins at the still visible 685nm, offering a dark red image.

The IR Pass filter reduces seeing effects. The negative influence of seeing (turbulences) isn't as prominent at longer wavelengths. As a result you get very high contrasts and an astonishing sharpness by stacking several images (e.g. using Giotto) captured with the IR Pass filter.

Using the IR Pass filter on the Deep-Sky This is another field of use for this filter. Many amateurs experiment with deep sky imaging, trying to make structures in the IR part of the spectrum visible.