Green Crack

at least 3-4 weeks, your stigmas turn to an amber or red, those are the hairs that are searching out. when most of these have turned color and die,, this is where you check the trichomes, they are those little balloons that are on the surface of the plant. find a jewelers loop to help you see the trichomes, these fill up with thc, when they are at their peek they are 50% amber 50% milky to amber. you can harvest when the ballons are milky and you will have more a head high. while the amber produces a couch lock in some strains and others it matures the thc in those buds. it sounds hard but it is not, look real close on your plant. hope this helps you figure your harvest out. i say around 3 weeks you should start looking at the thc ballons.

& looking at the image a little more closely, at least another month

Its a guess if you cant use a microscope, or at the very least, Take a photo through a magnifying glass? there is the train of thought that 3/4 of pistols go brown, that's done but trichome color is the most reliable, especially now paranoia & 'messy stone' is linked to immature trichomes. you need cloudy for 1st crop or main crop or wait until a 1/2 of your trichomes are amber, this allows for full 'couch lock' effect.