@Epicram, H.M. Gartley invented Harmonic Patterns in 1932.. After him, Scott Carney has done commendable work in this field inventing patterns like Crab, Bat, Shark, 5-0.
You can more information on Net and also read books by Scott Carney available on Amazon
@sanjoy.bose.it, The entry can be on the break of 1.130 of XA leg .. and 3.140 of BC leg... The level comes to around 9080 on the chart ( bottom of the shaded Potential Reversal Zone ).... On the Daily Nifty chart, there is also a big Supply Zone ( 9244-9070) from the previous highs made on 4th March 2015. A decisive break and closing below 9070 should be an ideal entry.
The target can be 61.8 % of CD leg as u said... comes to around 8400 roughly