I'm surprised that this topic got hits and yet nobody answered. Since it's such an easy question to answer and all.
The scope works by pressing the focus / slow button. This brings up a purple "lens" up, depending on which character you use. Any spirit that enters this scope gets "activated", and starts to float upwards unless you're using a certain character. The activation of spirits can be distinguished by a bubbling sound. Activated spirits, in addition to being a lot quicker to kill, also cancels out snowballs around them (i.e. explodes) much like a fairy does as opposed to well, not canceling out the bullets. If not destroyed after a certain period of time, the activated spirit will start flashing before disappearing, firing an aimed 3-way spread of bullets at you; 1 bullet if you're using a certain other character.
