While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of GT Advanced Technologies (NASDAQ: GTAT) popped 4% today after Dougherty initiated coverage on the solar and LED equipment specialist with a buy rating.

So what: Along with the bullish call, analyst Pierre Maccagno planted a price target of $29 on the stock, representing about 115% worth of upside to yesterday's close. So while momentum traders might be turned off by GT's recent price pullback, Maccagno's call could reflect a sense on Wall Street that the company's growth prospects are now too cheap to pass up.

Now what: Dougherty expects GT to grow its top line at a breakneck compounded annual rate of 93% from 2013 to 2016. "We believe GTAT will benefit as the sapphire market for consumer electronic products starts growing by taking share from gorilla glass as ASPs become competitive," said Maccagno. "Not only will they benefit from increased revenue potential but it will also position them as the most competitive cost producer of sapphire due to economies of scale and the learning curve experience." When you couple that upbeat outlook with GT's forward P/E in the midteens, it's easy to understand Dougherty's bullishness.