Hello,
I wondering if I use a laser during the activation phase to see if a ships is Inside the firing arc of another is allowed ?
This will help the current Player to determine the move (or decided if he do a barrel roll or get out of the arc).
Laser hasn't graduation and can't be consider has measuring.
Whereas, it's an "external tool" ...
Thanks !
You can only check a ship's firing arc when you're declaring its target in the combat phase, or when you use a pilot or upgrade ability that references a firing arc. So if you want to take the action on R7-T1, then you can (and should) check that you are in arc and range 1-2 of the opponent's ship. If you're just doing a barrel roll, however, you need to estimate the firing arcs by eye.
Maybe the laser would be considered illegal by some but that doesn't mean you can't walk around to visually check that firing arc. Get someplace you can line up the post with the corner of the base and there you should have a nice, and perfectly game legal, arc indicator to use although its accuracy may vary. Just be warned that while you are doing this some people might now think you are stalling although you are stalling even if you explain you are just trying to get things right and those same people would be the ones who complain if you threw down a laser line to judge the arc with instead.
You're damned if you do and damned if you don't.
I don't think you could be hit with a stalling warning if you state that you are going to check the arc visually and that requires you to walk around the table to different vantage points. If you took 5 minutes to figure it out then that's another matter.
Laser line is a form of measuring and is not allowed in a tournament venue unless there is a stipulated need for an arc check.
You shouldn't be hit with a stall warning although the basic point it is still much faster to use the laser and get a result that will be nearly identical.
But using a laser is certainly against the rules during the activation phase.
A laser is only replacing a range ruler for the sake of establishing firing arcs, therefore any rules that apply to when and when you can't use the ruler, will also apply to a laser.
The laser's beam will also touch the play surface and/or ships, which should disqualify it the same way as you would if you used your hands, a string, or any other means to check.
To sum up: NOOOOPE 
To sum up: NOOOOPE
So make sure you take all the time you need to visually make the calculations you need.
I had a similar question not long ago and got a heap of constructive feedback:
https://community.fantasyflightgames.com/topic/183595-check-firing-arc-question/
As a newer player, this is a recommendation that I have if you are playing a friendly game with an opponent that you are on very good terms with.
Use the laser pointer often.
We would both call a shot "in" or "out" first-- then pull out the pointer. It is amazing how quickly your Mark I eyeball skills get honed in that situation. You get dialed within millimeters after 10-20 games.
Obviously, don't do this during "normal play" and it is unthinkable during tournament play. This is more of a training wheels session to prepare you for those situations.