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: Investors in MKS Instruments (Nasdaq: MKSI) ended Wednesday in tears, crushed by news that the chip equipment maker is looking for Q3 earnings as low as $0.40 per share (versus Street estimates of $0.63.) But what a difference a day makes. In Thursday trading, the shares stomped their after-hours plunge, reversed course, and are now sitting 8% higher.

So what: In this world, there's news, and there's views. What started the sell-off yesterday was MKS's view that next quarter might turn out worse than it had hoped. The actual news yesterday, in contrast, was pretty good. Whatever may happen over the months to come, we know for a fact that MKS earned $0.73 in pro forma profits last quarter, a full dime ahead of what it had been expected to earn.

Now what: Personally, I've always been more partial to facts than conjecture in doing my own investing, so here's another couple-few facts for you. Fact: MKS costs just 9.2 times earnings today. Fact: Whatever happens in Q3, over the long-term analysts believe this company is capable of 20% annual earnings growth over the next five years. (OK -- that one's really an opinion, too. But at least it's a bigger-picture opinion.) Fact: MKS boasts a robust balance sheet loaded with nearly $480 million in cash -- nearly one-third of the company's market cap.

Admittedly, next quarter could be uglier than we'd like to see. Long-term, though, the company's prospects look strong, and it's got more than enough cash to tide it over until it can capitalize on those long-term prospects. Call me an optimist, but I think the investors who bought MKS today are the ones who are reading this story right.

Will Rich's optimism prove out, or will MKS plunge right back down into another sell-off tomorrow? Add it to your Watchlist and find out.

Fool contributor Rich Smith holds no position in any company mentioned. Click hereto see his holdings and a short bio.

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