you can use a magnifying glass as we do. Or even the bare eye. I harvest when just over 50% of the pistils turn ted, and about 80% of the trichomes turn amber in color. The more amber the more cannabanoid B variety you will have , which produces the couch lock cant get off your ass effect , compared to the translucent white crystals that are more common in sativas,and I find to be much more active, 'up' highs. Keep up the works man , good luck