SENSEX expiry 20 August 2026: what the 77,600 options did in the last 30 minutes
On Thursday 20 August 2026 the SENSEX strike nearest the index at 15:00 was 77,600. The index went from 77,572 at 15:00 to 77,538 at 15:30, down 34 points across the settle walk.
The at-the-money legs, 15:00 to 15:30
| Leg | 15:00 | High | Low | 15:30 | End vs 15:00 | Open interest |
|---|---|---|---|---|---|---|
| 77,600 CE | ₹51.1 | ₹51.2 15:00 | ₹0.1 15:30 | ₹0.1 | worthless | 10.3M → 10.4M |
| 77,600 PE | ₹91.8 | ₹163 15:24 | ₹62.5 15:30 | ₹62.5 | 0.7× | 6.1M → 3.5M |
Premium of the strike nearest the index at 15:00, sampled every ten seconds from the NSE option chain. Index values are the chain's own quote. Dotted verticals mark a pin-book flip on Gamma Terrain.
What happened
The 77,600 call was ₹51.1 at 15:00. It never traded meaningfully above its 15:00 price. Its low was ₹0.1 at 15:30, less than half of where it started the half hour. It ended at ₹0.1, worthless.
The 77,600 put was ₹91.8 at 15:00. Its high was ₹163 at 15:24. It ended at ₹62.5, 0.7× the 15:00 price. Open interest at the strike went from 6.1 million to 3.5 million, so positions were closed through the window.
Chain quotes were missing 15:15–15:16, 15:20–15:21: the exchange rate-limited the poll in the endgame, so the chart shows a hole there rather than a line. Highs and lows inside a hole are not known.
For context, across 21 NIFTY and SENSEX expiries measured to 2026-09-08, 15 of 42 at-the-money legs doubled at some point in this window, 26 lost half, and 13 ended at or above their 15:00 price. This page states what the tape did. It is not a recommendation to buy or sell anything.
Gamma Terrain shows the pin, the walls, the book read and every large print, tick by tick, on NIFTY and SENSEX.
The recap is the after-photo. The terrain is the window while it happens.
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