units 0

[Imp]

Depends on many factors Roman in no particular order.
1) Cover as in terrain they are in.
2) If fired to try & remain hidden just take 1 or 2 shots max.
3) Speed faster easier to find stationary harder, for searchers its the other way round.
4) Experience higher harder to find lower easier.
5) Suppresion if they are suppressed easier to find, if searchers are harder to find.
6) Unit type vehicles dont see as well esp tanks though in MBT TI tanks do not seem to bad. Some weapons have a higher chance of being seen when fired, ATGs ATGMs etc.

Having artillery dropping just in front of your advance helps a lot, if suppressed their shot is generally less accurate & they are easier to find as finding cover from the artillery to. The number of eyes is important the more the better

No hard & fast rules if you are suppressed or inexperienced might not notice an adjacent stationary unit taking a single shot.
Fast moving sniper using all his shots enough eyes & you might see him at 12 hexes or more.