My idea is MACD trends get at the internal goings on for the SPX that sometimes work better than specific point targets. I am still not certain why these patterns come up but they are consistent and they often repeat. The SPX is in some index goldilocks zone as far as this working, unlike the Dow and NDX, so here it can act as a market proxy using this method.
The top chart is the closeup view, and the bottom chart shows the larger megaphone shaped trends at work. These trends most often overlap in transition periods. Note the current channel within the major trend that we are in now - its resistance and support lines are parallel and the channel is quite steep. We just hit the support line and it is headed up. This downward channel replaces the up-facing channel which was exited on this recent drop in the index. I feel if this support line does not hold, the MACD could reach the support line of the larger megaphone trend, about -80s to -90s. If it should do so it would be a high probability event as far as reversals.