It is pretty visible in most instruments. If you're calculating a simple expected price of a stock at the open it's pretty normal to take the closing price from

It is pretty visible in most instruments. If you're calculating a simple expected price of a stock at the open it's pretty normal to take the closing price from the prior trade day and adjust it based on any corporate actions (dividends, splits, ...). Now whether or not this is actually the price that the instrument will trade at is a different story, but it's a good initial estimate. Market data and other activity will quickly inform you as to the actual price.