Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Cognex (Nasdaq: CGNX) got crushed today, down by as much as 13%, on the heels of an analyst downgrade.

So what: Piper Jaffray analyst Jagadish Iyer dropped the stock from "neutral" to "underweight," while also ratcheting down his price target from $30 to $27. That valuation would represent an additional 18% of downside even relative to today's low trade. He reduced his revenue and profit estimates for both 2012 and 2013.

Now what: The analyst believes that overall slowdowns in manufacturing in China, Europe, and the U.S. have yet to fully take their toll on Cognex, which sells machine vision products used in manufacturing processes. Cognex has been building up its presence in China, but Iyer believes sales in the region may fall by as much as 20% this year, while domestic conditions remain weak.

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Fool contributor Evan Niu holds no position in any company mentioned. Check out his holdings and a short bio. Motley Fool newsletter services have recommended buying shares of Cognex. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days. The Motley Fool has a disclosure policy.