NIB Sirius PC1 Planetary Contrast Filter - $50 (NOW $45) shipped. (retail is $66 plus shipping)
The Planetary filter has three peaks of high transmissions with the regions in between being heavily rejected. This sort of filtration is impossible with dye-in-glass filters.
This filter will show increased contrast and detail on various objects. The greater the spectral output of an object, the greater the effect.
(stock photo shown)