I'd say that you want it to get a bit lower than that before you turn it, otherwise it might change shape a bit as it dries.
I see that you live in Louisville, Tn and the RH is 70% right now and how dry the wood gets is relative to your local weather.
Do you have other known dry woods in your shop that you could measure and compare to?
I live in Wisconsin, and the RH is 93% today, but my "dry" woods stay between 8% and 11% MC. They will vary some, but when I use them when they are in that range I don't have any trouble. My shop and wood storage is in my detached, non-air conditioned garage, so it goes up and down with the ambient RH.
There are some other variables though, such as how thick will the actual wood be after you get done turning it? You may dry it out in the turning process just due to the heat from the friction of sanding and finishing. The thinner it is the faster it will dry.
You could also dry it some in your oven at a low temperature, I do that, but mainly for woods that I'm going to stabilize.
I hope this helps.
Tom