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 solar manufacturer SunPower (Nasdaq: SPWR) fell 10% today after the company released second-quarter earnings.

So what: The company actually beat earnings estimates by a wide margin in the second quarter with earnings per share reaching $0.08, well above the $0.09 loss analysts expected. But outlook was weaker than expected, leading to the drop.

Management now expects full-year revenue to be between $2.6 billion and $2.8 billion, a $200 million reduction on the top end. In the third quarter, the company expects to lose between $0.05 and $0.20, versus the penny profit analysts expected.

Now what: The reduced revenue was actually in line with estimates of $2.7 billion from analysts, but this was clearly the focus today. Management actually said that full-year adjusted earnings would be break-even or better, topping estimates of a $0.10 loss, but the third quarter will be significantly weaker than the fourth because of revenue recognition rules.

If you're bullish, you could take positive points from the report, and if you're bearish, the reduced guidance is what you'll be hanging your hat on today. Clearly the bears are taking over today, but I thought the second-quarter numbers were encouraging enough to stay long with for a (long-)long-term horizon.

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