Full Details from Amazon.com : http://www.amazon.com/gp/product/B0009E2762?tag=onigi-20

Orion 7816 Cooling Accelerator Fan for Large Reflector Telescopes

Speed up the cooling of your big reflector telescopes optics with this small quiet fan
Cooling your telescope optics significantly improves the quality of views through your reflector
You dont have to wait for lengthy telescope cooldown with this handy and effective cooling fan
Uses eight D-cell batteries not included
Battery life is about 13-14 hours of continuous operation