today she's 9 weeks old, 5 weeks in 12/12. i dont have a magnifying glass but im thinking of taking her down around 70% brown pistles.
Pistil color isn't a very accurate measure of when to harvest. Trichome color is really what you want to look at. You can pick up a 60x jewelers loupe for about $15 and that would save you a lot of hassle.
There was a thread a few months ago where a guy harvested by pistil color and the smoke was completely lack of THC. He finally looked at the trichome color on his harvest bud and they were all clear.
But.. if you must go by pistils, here is something that might help.