My First Grow

You could harvest now if you really want to but I would wait another week for a more longer lasting high, usually when aprox 80-90% of the white pistils have changed colour and showing whiplash. Going by your photo you have aprox 40-50% turned but your top pistils are still erect which means it's still going, this is only a estimate because this can vary within different strains so the way to know for sure is to inspect the trichomes but you'll need some sort of magnifier.