The Lumicon 1.25" Hydrogen-Beta Filter exclusively isolates the 9 nm-wide hydrogen-beta line of the light spectrum (486nm), to provide the maximum possible contrast on very faint nebulae.  You won't be able to find the celestial objects with the filter in place because it lets so little light pass, you would instead locate them and then attach the filter.  But though with the filter in place the view will appear tremendously dark, as your eye adapts you'll see much more contrast on the faint nebulous objects than is otherwise possible.
Nebulae is very faint-this filter is only recommended for use with 12" & larger telescopes, as anything smaller is not likely to gather enough light to take advantage of the filter.
View extremely faint nebulous objects such as Horsehead, Cocoon and California Nebulae
Strict quality control standards employed throughout production
Each filter individually inspected & inscribed with percentage of light transmittance of H-Beta emission line