Keltner Channels are a set of three lines that are overlaid on top of the price bars of a chart. As with other channel overlays, the outer two lines define a region that generally "contains" the price action and helps you determine if the prices are "too high" or "too low" relative to a specified moving average. Here is an example:
In the chart above, the Keltner Channels are the thin blue lines above and below the candlesticks on the chart. The red line corresponds to the 20-day Exponential Moving Average that defines the center of the channel. Notice that the candles generally appear to "bounce" off the blue channel lines are return to the red central line.
The original version of Keltner Channels was described by Chester W. Keltner in his 1960 bookHow to Make Money in Commodities. Keltner called his channel concept the "Ten-Day Moving Average Trading Rule" and defined it as a pair of lines positioned above and below a 10-day simple moving average of the chart's "typical price" - i.e., ( high + low + close ) / 3. The distance between the channel lines and the central line was defined as the 10-day simple moving average of the chart's "range" - i.e., high - low.
This original version of Keltner Channels was relatively easy to calculate in the days before computers and worked pretty well for trading commodities. As time passed, other channel systems - such as Bollinger Bands - became more popular. In the 1980s, Linda Raschke introduced a newer version of Keltner Channels that was based on the Exponential Moving Average and the Average True Range (ATR) indicator. StockCharts.com uses this more modern version of Keltner Channels.
In the modern version of Keltner Channels, the central line is (typically) a 20-period Exponential Moving Average. The upper and lower bands are drawn at an equal distance from the central line. The distance is defined as a specified multiple (typically 2x) of the ATR(10) indicator.
In SharpCharts, the Keltner Channels take three parameters. The first one is the period of the central EMA. The second one is the multiplier for the bands. The last one is the period of the ATR indicator. The default parameter values are "20,2.0,10".
In the chart above, we've added the ATR(10) indicator below the price plot. You can see how the Keltner Channel expands as the ATR(10) value rises and contracts when it shrinks.