Based on your pics it looks like you're about ready. Mid October is probably the latest you want to harvest outdoor (most strains are ready late sept, early oct.).
Get a magnifying glass and look at the trichomes as stated by others. Some strains don't really turn amber, and by the time they do it's too late for harvest. Generally, the more trichomes which are amber, the more sedative qualities you'll have. But as long as your trichomes are all at least milky white, and especially if you see some amber. You'll be ready for harvest.
Another point to note is that proper curing over a length of time, in my opinion, is just as important as waiting for the trichomes. Slow cure in mason jars for at least 3 months and you'll notice a dramatic increase in sedative quality. I'm sure you'll notice as you make your way through it. The stuff that sits longer just keeps getting better.
