00What a field is
A field is one observation with fixed terms: a target stock token, a comparison stock token, plate 1 and plate 2 (two Fridays at 19:00 UTC), a gain, a saturation and a fee. The observer who opens it posts the full well, GAIN × SATURATE in USDG, before anyone can buy.
The buyer pays the fee once, before plate 1. After plate 2 the field pays the buyer GAIN × min(|ln r|, SATURATE) from the well, and the rest of the well goes back to the observer. Up or down does not matter. Only the size of the target's move against the comparison does.
01Why divide
An astronomer never measures one star alone. Haze, moonlight and the thickness of the air dim every star on the plate together, so the star is measured against a comparison on the same plate and the sky drops out. This is differential photometry.
Stock tokens sit under one sky too. When the market turns, they move together. Dividing the target by a comparison removes what moved both and leaves the target's own move.
ln r = ln(T₂/T₁) − ln(C₂/C₁)
a move shared by both cancels exactly
02Why the logarithm
On a log scale, up and down are the same size: a move from 100 to 110 and back from 110 to 100 are ±0.0953. That is why a field can pay on |ln r| and be indifferent to direction. Astronomers use the same scale for brightness; a magnitude is a log of a brightness ratio.
Units: magnitude reports ln-ratio. It does not report astronomical magnitudes. If you want them, Δm = −1.0857 × ln r.
03Two plates, proven
A plate is the value each Chainlink feed was holding at the plate time T. It is proven with two consecutive rounds of the same phase: round k with updatedAt ≤ T, and round k+1 with updatedAt > T. The caller cannot pick a convenient older round, because the next round must start after T.
- The held value may be up to 24 hours 10 minutes old at T. Older than that, the plate is not valid.
- At plate 1, round k must have been posted after the sale ended, so nobody buys knowing the starting value.
- Proofs use rounds of the phase each feed was on when the field was opened.
- Proofs can be submitted for seven days after plate 2. The next round can arrive late; on the plates on record it took up to 54 hours after a Friday close.
- The two legs are read at the same T, not at the same instant of trading. A field pays on held feed values, not on simultaneous market prices.
04Gain, saturation, full well
GAIN is the USDG paid per 1.0 of |ln r|. SATURATE caps |ln r|, the way a detector saturates. The full well, GAIN × SATURATE, is the most the field can ever pay, and the observer posts all of it before the field can be bought.
observer = FULLWELL − payout
payout + observer = FULLWELL, always
Recorded replay: GAIN 1000, SATURATE 0.20, FULLWELL 200 USDG. NVDA ÷ SPY from 30 Oct to 06 Nov: ln r = −0.057368, so the holder receives 57.367831 USDG and the observer 142.632169 USDG. Amounts are integer micro-USDG; payouts round down and the remainder stays with the observer.
05The fee
The observer sets the fee. The buyer pays it once, before plate 1, and it goes to the observer at the sale. Nothing accrues after: no carry, no top-up, no margin, and nobody can close the field early. The fee is a price the observer chose, not a price magnitude computes or vouches for.
The sale ends when the observer says, 25 hours before plate 1 at the latest, and the fee is a quote that holds until then.
06Reduction and claims
After plate 2, anyone can submit the four proofs (two legs × two plates). The contract checks them, computes ln r, and splits the well. The holder and the observer each claim their own part, separately.
07Clouded out
If no valid proof for a plate arrives within seven days of plate 2, a held value is older than 24 hours 10 minutes, or the value held at plate 1 was posted before the sale ended, the night is clouded out. Anyone can call the return: the buyer gets the fee back from the well, the observer gets the rest of the well. Both end where they started, apart from gas and the MAG spent to open.
08Opening a field, and $MAG
Every field on the sky is opened by an observer who chooses the target, the comparison, the plates, the gain, the saturation and the fee; posts the full well in USDG; and spends MAG. Without MAG, no field opens. Buying a field needs no MAG, and a field already sold pays its terms whatever happens to MAG.
The amount of MAG spent per field is a launch parameter. MAG does not take a share of fees or payouts.
09The observation header
Every field is recorded as a header in the FITS card format astronomers have used since 1981: 80-character cards, an 8-character keyword, a value, a comment. The same record is published as JSON.
10What it does not do
A plate is the value each feed was holding at the plate time. It is not the market price at that instant.
Only two plates are read. A gap that opened and closed between them is not paid.
The fee is the observer's price. magnitude does not promise it is fair.
11Trust assumptions
- Plates depend on the Chainlink tokenized-equity feeds on Robinhood Chain continuing to report.
- USDG's issuer can pause transfers or freeze an address. While it does, claims and returns in USDG wait.
- Block time, and so every deadline here, is set by the Robinhood Chain sequencer.
- Feed values carry each token's dividend and split multiplier; magnitude does not apply it again.