Since I heard about one dozen different explanaitions about this issue, I'd like to have a solid opinion on this issue.

Is it allowed to measure distances or check arc whenever you want (especially during the activation phase)?

I'd say no, at least that's how we played it so far. The only thing that's probably halfway legal would be announcing a target lock onto something you assume you have not in range. Then you can measure distance to that ship, TL fails, then announce another action.

Also, is it allowed to estimate with your fingers where a ship will end after a movement or action like barrelroll or push?

Again, I'd say no ...

Thanks a lot for everybody answering

/edit: assuming playing with tournament rules.

No, no, and no.

You are only ever allowed to measure when:

- Attempting to take the Target Lock Action

- checking requirements for a range-based ability (i.e. Howlrunner, Biggs).

- firing with the active ship.

And, to be even more specific, you have you take that target lock if it is in range.

- firing with the active ship.