Hello BigPipGrabber, and welcome to our forums.
What KevinLaCoste and The LastBear say is very valid: indeed, the art of understanding not only the impact of news releases
on the two currencies within a pair, but also how the news item is manipulated by institution to acquire or liquidate ‘stock’,
is very complex and indeed treacherous.
To answer your question, I wondered how best I would approach this myself: as for my own trading with synthetic pairs,
like the EUR/GBP, I have learnt that currency correlation is a great aid, although it can work better on longer-term than
on shorter-term trading objectives: given that EUR/AUD is a pair made of the ‘fusion’ of EUR/USD and AUD/USD, it pays
to put the three charts in the same screen and compare how they move in relation to one another, over time:
You can see how, with minor deviations, EUR/AUD moves as a mirror image to both AUD/USD and EUR/USD: bearing
in mind that this is a monthly chart, encompassing many years of price action, it is still giving truth to a strong negative
correlation between EUR/AUD and AUD/USD. However, when dealing with shorter-term moves, especially when trading
the news (e.g. on a five-minute chart), this correlation may break and the two pairs may move not in opposite directions
but in tandem, which is why I prefer looking at longer-term charts when seeing how the ‘correct’ correlation relationship
is working over time.
If in doubt, use the currency correlation map by Oanda, for example, to see how EUR/AUD’s correlation is holding with
regard to its ‘root’ pairs, EUR/USD and AUD/USD:
Forex Correlation | Currency Correlation Chart | OANDA fxTrade Europe
Here is a screenshot from it:
The map shows that, on a monthly time-frame, EUR/AUD has a very strong negative correlation to EUR/USD at the moment,
but on the same time-frame there is a very weak relationship to the AUD/USD… This tallies with what you may have
witnessed yourself, i.e. expecting EUR/AUD to go up when AUD/USD went down, but there being a slight divergence in
‘normal’ correlation.
I hope this helps…
PS: the chart was from my FXCM web-based trading station.