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re: F6 -- correct the onset, the sweep starts MIDWAY not just before the plate

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The port challenged two statements of mine as mutually inconsistent and
refused to guess which I meant. They were right to. Answering with the
clock-free quantity they proposed:

  (onset - title start) / (plate - title start) = 0.489 / 0.507  (3.7% apart)

So the onset is at the MIDPOINT. That refutes the port's implemented 0.2 and
my own summary's "shortly before the plate" (~0.85) alike.

Root cause of my error: the ratio measurement was right, but I converted it
to title units through the plate's declared 12-unit ramp and wrote the
summary from the conversion. That calibration makes title-start..plate 75
units where the data declares the plate at t=238 -- 3.2x out, not the 1.75x
this page reported. All title-unit figures withdrawn; the ratios never
needed a clock.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jc4pciRArGHfxGGhEbwp5t
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docs/re/f6-unit9-sweep-period-and-onset.md
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@@ -38,19 +38,36 @@ and gave an 8% spread where this gives 0.35%.
The cycle boundary is unambiguous: the sweep enters at `x=-1.540` and wraps from
`x=+1.840` back to `x=-1.540`, so first-appearance→wrap is one whole period.
Calibrating the baseline with the plate's declared 12-unit ramp (238→250) puts
it at ~48–52 title units, so in title units: **period ≈ 670–720**, **the sweep
leads the plate by ≈ 40**.
🔴 **Do not convert these to title units.** Calibrating via the plate's declared
12-unit ramp gives a title clock that puts `title start → plate` at 75 units
against a declared 238 — see below. The ratios stand alone; the conversion does
not.
## What this says about F6
**The sweep does not start at title `t=0`, and it does not start exactly with the
plate.** It starts a short, reproducible interval *before* the plate — ~0.8 of
the baseline, ≈40 title units, well under a second.
**The sweep starts about HALFWAY between the title's first drawn element and the
plate's appearance.** Clock-free, and the quantity to implement against:
So the human's report is approximately right and the port's behaviour is not: at
`t=0` the port starts it roughly 200 units early. The human could not have seen a
40-unit lead as separate from the plate, and did not claim to.
| | f6 | f6b | agreement |
|---|---|---|---|
| **(onset − title start) / (plate − title start)** | **0.489** | **0.507** | **3.7%** |
So it starts neither at `t=0` (the port's behaviour) nor just before the plate.
🔴 **This corrects an earlier version of this page**, which said "≈40 title
units, well under a second" and "at `t=0` the port is ~200 units early". Both
came from converting the ratio into title units through the plate's declared
12-unit ramp — the same calibration this page already flags as conflicted. The
conflict is worse than stated: `title start → plate` measures **75 title units**
through that calibration, where the declared data puts the plate at `t=238`.
**3.2× out, not 1.75×.**
**Every title-unit figure on this page is withdrawn.** The ratios never needed a
clock and are unaffected.
⚠️ Note the two ratios describe the same fact and do not conflict: the baseline
(`-0.740` → plate) is only ~64% of `title start → plate`, so 0.79 baselines and
0.51 title-spans are the same interval measured against different rulers.
## 🟡 A conflict I did not smooth