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 satellite-imagery expert DigitalGlobe (NYSE: DGI) fell out of their orbit today, losing as much as 20% in intraday trading before closing down 10%.

So what: Analysts at Wall Street firm Dougherty & Co. may have a bullish buy rating on DigitalGlobe shares, but it looks like they helped drive today's less-than-bullish action. Dougherty left the buy rating in place, but dropped its price target on DigitalGlobe's shares nearly 40%, from $38 to $23.

Now what: DigitalGlobe and competitor GeoEye (Nasdaq: GEOY) have both been languishing under investor concerns that a tighter defense budget may mean less business coming their way. Those concerns set up events like today's price-target cut by Dougherty to have a severe impact on DigitalGlobe's stock -- as long as investors think there's a lot of potential upside in the stock, they may be willing to brave the risks, but if that upside is seeming to evaporate, the stock may not look quite so attractive anymore.

That said, this is just the view of a single research firm, so investors need to take it with a grain of salt. While it could be a great reason for current investors to revisit their own assumptions and price targets, the price-target revision by itself is probably a bad reason to sell.

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