Calling an exact price can be difficult. Although indicators can't tell us exact prices or dates, they can be a great resource for deciding when to enter a market. The for Bitcoin has followed a channel for nearly a year now. Based on the previous two corrections, the market should reverse when the touches the bottom of this channel, currently 30.
The second indicator to watch is the moving average. Bitcoin appears to reverse after tapping the 130 day , though you can use the 100 day for a more conservative entry point.
As Bitcoin drops, keep in mind that this is a young, unregulated market. It can act irrationally and can be easily manipulated. Always use caution and weigh the risks.
Note: The previous two runs have hit the upper resistance line twice before correcting. The current run may only be in wave 4 of 5, as it has only touched this resistance once. If the double tap pattern continues, a rally to 8200 is possible.