Aster Stock Perpetual Contracts & EWMA-Smoothed Mark Price

Aster Perpetuals now supports Stock Perpetual Contracts, enabling users to trade perpetual futures on U.S. and Hong Kong-listed stocks fully settled in USDT. Traders can open both long and short positions with up to 50x leverage and flexible leverage selection during order placement.

To improve trading stability during low-liquidity periods such as overnight sessions, weekends, and public holidays, Aster has introduced an EWMA-Smoothed Mark Price mechanism for stock perpetual contracts.

Mark Price

On Aster Perpetuals, the Mark Price is used as the reference price for:

* Unrealized PnL calculations * Liquidation triggers * Margin evaluation

The Mark Price is designed to reduce unnecessary liquidations caused by abnormal volatility or temporary price manipulation, making it more stable than relying solely on the last traded price.

Index Price

Aster sources index prices from multiple providers, including the Pyth Oracle, to ensure reliable pricing data for settlement and mark price calculations.

Standard Mark Price Mode

Under standard conditions, the Mark Price is calculated as the median of the following three values:

Price 1

Funding-adjusted index price:

Price_1=Index\ Price\times\left(1+Funding\ Rate\times\frac{Time\ to\ Next\ Funding}{Funding\ Interval}\right)

Price 2

Index price plus the 5-minute moving average deviation between the order book midpoint and the index price:

Price_2=Index\ Price+MA_5\left(\frac{Bid_1+Ask_1}{2}-Index\ Price\right)

The 5-minute moving average is sampled every minute over a rolling 5-minute window.

Contract Price

The current traded contract price on the exchange.

The system then selects the median of these three values as the final Mark Price.

For example:

If:

Price 1 < Price 2 < Contract Price

then Price 2 becomes the Mark Price.

This mechanism helps filter out abnormal short-term volatility while still reflecting actual market conditions.

EWMA-Smoothed Mark Price Mode

During low-liquidity periods, Aster replaces the raw Contract Price component with an Exponentially Weighted Moving Average (EWMA) of the last traded price.

This reduces the impact of sudden thin-market price spikes.

The EWMA price is calculated using the following formula:

EWMA_t=(1-\beta)\cdot LastTrade_t+\beta\cdot EWMA_{t-1}

Where:

\beta=e^{-1/1600}

If no trade occurs during a given second, the previous EWMA value is carried forward until a new trade is executed.

Under EWMA mode, the Mark Price becomes the median of:

* Price 1 * Price 2 * EWMA Price

For example:

If:

Price 1 < EWMA Price < Price 2

then the EWMA Price becomes the Mark Price.

Purpose of EWMA Smoothing

The EWMA mechanism is designed to:

* Reduce unnecessary liquidations * Minimize the impact of temporary price spikes * Improve market stability during low-volume sessions * Create a smoother trading experience for leveraged traders

This is especially important for stock perpetual products, where liquidity conditions can vary significantly outside regular stock market hours.

Risk Reminder

Aster reserves the right to modify trading parameters at any time, including:

* Funding rates * Minimum price increments * Maximum leverage * Risk limits * Maintenance margin requirements

Users are encouraged to review the official trading rules and risk disclosures before participating in stock perpetual markets.