
A-B= 870-830. This was a 40pt move.
B-C= 830-850. So far this is a 50% retracement of the move down.
C-D=850-40pts=810. This would complete the AB=CD pattern.
Now this pattern would be voided if we got above 855, since the AB=CD move can only make retracements of .382, .50, .618 or .786. Above 855 is more then a 78.6% retracement.
I think if we combine this analysis, with the MEGA B, the candlestick patterns mentioned. This scenario is more then likely and you have a nice out above 855 if you are more inclined to hold it 861 could be an out. if you wanted to take it. Right now SPY is @ 84.50, so you risk 1.05 to possibly get 81.00 or 3.50. Not a bad trade.