Parabolic SAR accelerated
Marks bars of a long, accelerating uptrend, after price has kept making new highs since the trend turned up.
A Parabolic SAR trail runs on the closes, highs and lows, but only a flag is output; the trail itself is not drawn. In an uptrend, each bar whose high beats the trend's highest high raises the acceleration factor (AF) by af_increment, up to af_max, and a close below the trail flips the trend down and resets AF to af_start. The flag is on only while the trend is up and AF has reached 80% of af_max, which at defaults takes eight new highs; it stays on until the trend flips. Despite the name, it does not look for a parabolic price shape.
How to read it
- Markers sit on every bar the flag is on, so one uptrend shows as a run of markers. Count runs, not dots.
- On the sample (SPY one-minute bars, September 2026) it was on for about 4% of bars, with 113 events, roughly 5 a day.
- A run can only end when a close breaks the trail. That break is not drawn, so the end of a run is where the trend reversed.
- No markers means a downtrend or an uptrend that has not yet matured. It does not mean a bearish signal.
What it outputs
- Accelerated uptrend
- True on bars in an uptrend where AF has reached 80% of af_max. False in downtrends and early uptrends; the bar that flips the trend shows nothing.
When it fires
Fires on each bar in an uptrend where AF has reached 80% of af_max: at defaults, after eight new highs since the trend turned up. It means price has kept printing new highs with the trail still below it. The state holds for the whole run and switches off only when a close breaks the trail.
Settings
- af_start
- Starting AF after every trend flip (default 0.02, the textbook value). Raising it tightens the trail from the first bar of each trend; at 0.16 or more, with default af_max, the flag is on from the first uptrend bar. Lowering it loosens the early trail.
- af_increment
- AF added on each new high in an uptrend (default 0.02). Raising it reaches the flag threshold in fewer highs, and 0.04 needs four. Lowering it delays both the flag and the tightening of the trail: 0.01 needs fifteen new highs.
- af_max
- Ceiling on AF (default 0.2). The flag turns on at 80% of this, so 0.1 needs four new highs and 0.3 needs twelve. A higher ceiling lets the trail close in faster on long moves, so pullbacks are more likely to flip the trend.
Pitfalls
- It is a state, not an entry: at defaults price has already made eight new highs by the time it is on, so much of the move is behind it.
- The reversal is not textbook: a flip sets the SAR to the previous bar's high or low, not the trend's extreme point, and the stored previous-bar values are one bar stale after a flip.
- Negative values pass the catalog range but push the trail the wrong way; keep all three params positive.