The best way to know when to harvest is with a 60x microscope.. you can pick up at any radio shack for $13 dollars! I have one and it is perfect for looking at the trichs.. its 60x - 100x.. if I was you I would try to pick one up as soon as possible.. But I guess if you cant then I suppose you could judge it by the hairs but that seems a lil shady to me.... good luck bro! plants look greeeaaat!