By definition, a true #altszn can be seen in the BTC dominance chart. 
The #BTCD chart shows where money is spread in the market. Concentrated in #BTC, or in others (alts!) 

As the dominance declines (shown by the green arrows)  money generally starts moving into alts. This is when the 'real' alt season starts.

Remember our cashed up bags earlier this year? 
Yeah, BTCD hadn't even started declining yet... 👀🚀
#altszn #BTCD #BTC