Just some thoughts from an amateur. BTC breakdown seems to be heading for an intersection between 3 points crossing at 4400k:
- Long term trend line from when BTC was first listed on Coinbase - 0.786 fib retracement level for the same period - Symmetrical distance from July's high
As an aside, the same analysis on the bit stamp chart shows BTC breaking down through the long term support as it intersected with the long term trend line on stamp.