Ethereum's chart is useful as it is the No.1 altcoin (in value) and provides the backbone for many coins that run on its protocol.
Looking at the the charts, the coloured boxes highlight Bitcoin's phases and the clear boxes show Bitcoin's pullbacks to the upside. Each corrective oscillation so far has peaked at 0.618 fib of previous. Price bands have decreased uniformly with each oscillation.
Looking at the Ethereum chart ETHBTC below: From 7th April Ethereum provided a good swing trading opportunity and it rallied through Bitcoin's phase. It also increased a little during Bitcoin's pullbacks. On the downside of Bitcoin's oscillation, Ethereum lost value to Bitcoin , as can be expected.
The sentiment changed as Bitcoin rallied into another oscillation beginning on the 29th June. Ethereum lost significant value to Bitcoin as it rallied, and then continued to lose value as Bitcoin moved to the downside. From there (10th August), Bitcoin pulled back until its current value today.
Now looking at ETHUSD below: On the previous oscillation, when Bitcoin pulled back Ethereum responded positively, moving a little to the upside. Now on the current pullback, Ethereum continues to plummet lower and has now passed back into pre-2018 values, having lost all of its value from the 2018 'altcoin season.' It is also passing through longterm support held from August - November 2017.
Ethereum (as many other coins) is showing a perspective. Although Bitcoin has rallied in late June and most of July, Ethereum has not and apart from a few shallow pullbacks, it has moved to the downside since 6th-May. ETHBTC/ ETHUSD has now passed through a death cross on the 50/200smma on the . Bitcoin looks set to do the same shortly.
Altcoins momentum is increasing to the downside with less relief rallies and shallow pull backs. Bitcoin however is oscillating within a narrowing price band. Will Bitcoin follow Ethereum into a more impulsive phase to the downside? Will Altcoins capitulate in reaction to this? Let's see.
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If Bitcoin is about to form the second half of a now rather elongated oscillation (see related idea) then many of the Altcoins will (likely) follow and lose to Bitcoin and will not have had any significant relief since early May.
The flip-side of this is that if Bitcoin were to have another corrective relief rally after another impulse down, Altcoins (of worth) could be ready to have a significant rally against Bitcoin.