This morning, Citigroup (NYSE:C) raised its estimates for Apple’s (NASDAQ:AAPL) June, September and December quarters citing stronger than expected iPhone demand. The firm's June quarter estimate is now $6.34, making it comfortable owning the stock into the results. Citi calls Apple one of its highest conviction stock ideas for the back half of 2011 and raised its price target for shares to $450 from $435.Apple has a potential upside of 29.3% based on a current price of $353.75 and an average consensus analyst price target of $457.24.Apple is currently above its 50-day moving average (MA) of $338.61 and above its 200-day of $331.28. In the last five trading sessions, the 50-day MA has remained constant while the 200-day MA has risen 0.3%.