On the side topic of the perception/vigilance check, I can think of a few ways a character might have to be able to reliably spot something at extreme range. Granted, if the sniper was using stealth, like a proper sniper, it would take an action and a successful roll to find him.
Some items that could trivialize the finding of a sniper are:
- electrobinoculars (much better than macrobinoculars)
- the enhanced optics suite armor attachment
- a general purpose scanner or a combat scanner
- the integrated scanner armor attachment