Why 09:30
On five years of NQ, 55.7% of first touches on a prior-VWAP grid land in the Asian session. Only 27.2% in RTH. On the 0.236 it is 74.5% Asia. Those levels are spent before New York opens. Anchoring on the cash open roughly doubles the number of RTH first touches.
The scale is last night
Sigma is the overnight high-low range, times a factor, divided by the open. Garman-Klass from 5 to 250 days was a non-monotonic mess. The signature of noise, not a horizon worth tuning. The overnight range was the most consistent of the lot across years.
Seven each way
0.236, 0.382, 0.618, 0.786, 1.000, 1.272, 1.618. Continuous compounding from the open. Historical days can stay on the chart. The live grid does not recompute after the bell.
How to stand in it
The inner harmonics are pullbacks. 1σ is the day’s ordinary limit. 1.272 and 1.618 are extensions: rejection and terminal. The study is a map, not an entry script. You already know how you fade or follow. This tells you which prices are still unused.