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 high-tech manufacturing equipment builder Veeco Instruments (Nasdaq: VECO) fell as much as 13% this morning on very heavy volume.

So what: LED specialist Aixtron (Nasdaq: AIXG) just reduced its revenue and margin guidance because of plummeting unit prices and several delayed orders. Veeco makes a market in LED manufacturing equipment; ergo, bad industry news produces an uncomfortably close haircut.

Now what: The entire LED industry stumbled on Aixtron's warning, including an 8% drop for materials provider AXT (Nasdaq: AXTI), a 7% drop at worst for fellow equipment designer CVD Equipment (NYSE: CVV), and of course an 18% plunge for Aixtron itself. The long-term promise of LED lighting remains solid, but investors are quick to sell at the first hint of short-term trouble. Unless you truly believe that Universal Display (Nasdaq: PANL) and its OLED lighting products will kill LED lights entirely -- which is a charming but silly notion -- you're better off treating these knee-jerk panics as buying opportunities. This is exactly the kind of enriching event that watchlists were made for.

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