you likely have about 2 to 3 more weeks for the best results, you could harvest right now but the buzz wont be as full and yield will be lost, it still has pistols that are very much alive and you can see from the picture many clear trichomes but mostly milky, I say two or three weeks but really it is any day now that you will start to see major changes but I am not a psychic, it is best when they get this look yours has for you to just wait 2 to 3 weeks and it will be fine smoke regardless, goodjob my friend and congratulations.
Keep an eye on the overall hue of the plant and you will see it get darker as the trichomes amber and more pistols recede, notice the sparkle will go away and the plant looks snow covered instead of shiny as the trichomes turn from clear & milky into opaque and amber. You really don't need a scope to see this after some experience but it sure can help you learn about your plants in particular and the maturation process.
here is a good read on cannabis maturation:
http://www.kindgreenbuds.com/marijuana-grow-guide/cannabis_maturation_harvesting.html