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 ReneSola (NYSE:SOL) popped by more than 16% on high volume during intra-day trading today after Zacks Investment Research announced it had upgraded the stock to its highest rating, "Zacks Rank #1 (Strong Buy)."

So what: There don't seem to be any concrete new business developments coming from the solar company today, so the upgrade appears to be the culprit. Keep in mind, however, that Zacks often relies primarily on automated algorithms to make its calls, which are then supplemented with company-specific information. While that doesn't automatically make the call a bad one, investors might be wise to take these upgrades with a grain of salt.

Now what: It's worth noting that shares of ReneSola have only now just recovered to the point at which they stood last month -- that is, before the company shocked investors on September 11 by pricing their $70 million registered stock offering around 15% below the previous day's close. As fellow Fool Brian Pacampara pointed out at the time, that served "as yet another reminder of ReneSola's precarious financial position," which was punctuated by its continued losses and still-heavy debt load.

Still, shares of ReneSola have more than tripled so far in 2013, riding a wave of momentum on better than expected shipments and increased financial guidance. Though this one's still a bit too risky for me, I'll admit speculative investors could be rewarded handsomely if ReneSola can keep up it up long enough to achieve sustained long-term profitability.

Fool contributor Steve Symington has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.