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 IPG Photonics Corporation (NASDAQ:IPGP) finished the trading day on Tuesday with close to a 6% loss after dropping to a 10% loss early in the morning. Investors seem unhappy with the fact that IPG's upcoming quarter is looking a little soft, despite the fact that the company bested top-line expectations for its fiscal first quarter.

So what: IPG's first-quarter revenue came in at $170.6 million, a 20% year-over-year improvement that also cleared analyst expectations of $168.1 million in revenue. The company's bottom line showed $0.77 in earnings per share, which matched analyst expectations. Looking ahead, IPG now expects to generate between $173 million and $188 million in revenue for the second quarter, which will result in a range of $0.77-$0.92 in EPS. Analysts had modeled a second quarter with $187.1 million in revenue and $0.90 in EPS, so the midpoints of IPG's guidance -- $180.2 million in revenue and $0.85 in EPS -- fall beneath those estimates on both counts.

Now what: It's hard to call this bad guidance, as it IPG's midpoints would represent year-over-year growth of 7% on the top line and 6% on the bottom line. However, this is not particularly strong growth for a company that just posted a year-over-year growth rate of 20% in revenue and 15% in EPS. Slowing growth is always a concern, particularly for a company that's seen its share prices rise primarily on P/E expansion over the past year. Tread cautiously with IPG. It's not a screaming buy today, but it's hardly in the nosebleed-P/E territory it once occupied, either.

Alex Planes has no position in any stocks mentioned. The Motley Fool recommends IPG Photonics. The Motley Fool owns shares of IPG Photonics. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.