Filters are used to enhance contrast and thus bring out specific details that would otherwise be difficult to discern.
See
http://www.lumicon.com/store/pg/15-L...a-Filters.aspx (toward bottom of page) and
http://vernonscope.com/index.php?rou...tegory&path=70 (click on each filter for more detailed description of each.
Note Vernonscope filters only fit Brandon eyepieces and Daikin Barlows. An adaptor is needed for 1.25" eyepieces. (Thread is different).
Do not hesitate in using your narrowband filter on Jupiter as it looks amazing in O-III and H-Beta!