Definitely at the point you should be scoping to see the trichomes... the exact point you harvest depends on personal preference.. so observe ripeness, take note, and test it out... try something more or less ripe next time and figure our your preference. There is a window of time, not an exact moment.
You'll find trichomes are not 100% consistent in their progression. May need more than 1 way to keep your harvest timing consistent.