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 high-tech manufacturer IPG Photonics (NASDAQ:IPGP) fell 12%, after delivering a disappointing earnings report.

So what: Third quarter revenue rose 21% to $156.4 million and earnings per share were $0.81, both ahead of estimates. But guidance often trumps the previous quarter, and IPG doesn't seem to think the fourth quarter will be as good as analysts do. In the quarter, the company sees revenue of $140 million to $150 million, and earnings of $0.65 to $0.75 per share. Analysts had expected revenue of $155.7 million, and earnings of $0.81 per share.

Now what: The guidance miss was more than enough to knock down shares today. But, before you throw out the stock for the guidance numbers, remember that operations continue to improve, even if management sees a tough fourth quarter due to the macro environment. Shares are now trading at 16 times forward earnings estimates and, if shares fall a little further, the stock could be a great value for the long-term investor.

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