Frames with narrow band filter have limitation of information. We just use these filters for this. Alone they hidden many informations.
They are very important when used as complement to a RGB image. To boost some details or structures.
They can be used to create some special presentation of the object. Bi-color, Hubble palette, ESO palette, crazy palette ... Some are very useful to show specifc details of object. Others, only to present a beautiful and impressive photo.
For amateurs the H alfa, O 3 and S 2 are most usual. But some others filters more professional brings amazing and astonishing informations:
http://www.nasa.gov/chandra/multimed...l#.VB66yVdJdNt