[Eric Johnson]

Just a few thoughts on the technical value of using an S&P continuous futures chart for stock market prep work, and monitoring it. For me it is worth the investment to use a backfill source that includes this chart, even if I am not trading futures.
First of all, there is so much data reflecting foreign market moves, news announcements, or after hours earnings. More importantly is the continuity of the establishing of trendlines, support and resistance levels, and also for technical indicators. Most oscillators are relying on a number of back bars. To jump in at market opening, or gaps between stock trading hours, can distort or make indicators useless for the nearly the first hour of trading. More importantly for me, is that my personal system of overbought, oversold, paintbars just show up clearer on the futures chart. This is helpful for whatever I am trading, assuming it is an equity that relates to the index movement.
I am observant of enough volume and reasonable volatility when I use indicators. To effectively use oscillator extreme conditions as an indicator, I dismiss the signal if there is an unusual price gap, very low volume, unusually narrow trading range, or extreme volatility. I am also very cautious about the first and last 30 minutes of trading, due to "bulldozer" stampedes, rather than a technical traders or oscillating market environment . Anyhow hope this of use to someone out there.