Sighting Question

[Gila]

Can anyone help me with a little someting I don't quite understand about the sighting rules? I'm often attacked by units I can't see, I don't mean units that haven't been spotted I mean by units that are in hexes my target unit can't even draw a line of sight to (ie if I right click in the direction of the firer he is occupying a dark hex). In a game I played last night I took fire from an initially unspotted enemy tank. After he fired a few shots he somehow appeared on the map even though he was in a dark hex. In my turn his hex was still dark to the unit he had fired on and I couldn't target him with it although he had had no problem targetting me. Both units were tanks of the same size and had the same level of sights. Not sure I understand whats going on here.

Thanks in advance.

Elevation and good cover in a hull down position, come to play big time here.
Remember,if you are higher ground (open ground) and the tank firing at you is hull down in a depression,all you will be able to spot is the fact you were fired on the first time.
Maybe that's why you saw it the next turn but was still unable to return fire,all you have is the small harder top of the turret and he's got your larger soft underbelly.
That's why you can ambush a Tiger very effectivly by having a smaller tank(s) or infrny waiting on a lower slope of a hill.