If the the 3 and 8 ma is very high above the 50 ma, 100 ma, 200 ma, then it shows that there is very good short term up momentum, so when the market comes down into the gap between the 3 ma and the 8 ma, you can enter long.
Another (similar, closely related, only slightly different) method is to do essentially the same thing, but waiting for the market to go back above the gap again, after the dip into it, before entering long. Fewer trades, higher win-rate, not necessarily more profit.
It's an intelligent and realistic way of using indicators to assist you in "buying the dips in an uptrend" (and vice-versa for short positions, of course).
(It's also notable for being far more sensible, practicable and reasonable than the ways that many people are trying to use moving averages, by entering trades on the basis of their crossovers!).
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