Solar Light Company, Inc. announces the updated Model 540 Microtops II Sunphotometer. The Model 540 is a light weight, portable 5 channel meter for measuring aerosol optical thickness, direct solar irradiance, and water vapor column easily, accurately and dependably. This multi-spectral instrument is designed to measure direct solar irradiance at all selected wavelengths. It then uses this information to provide atmospheric properties, such as aerosol optical thickness and water vapor column. Standard wavelengths to choose from are 340nm, 380nm, 440nm, 500nm, 675nm, 870nm, 936nm, and 1020nm. To facilitate field operation, Solar Light offers many options for this model, including a rugged carrying case and Garmin GPS. The unit features accuracy comparable to much larger and more expensive instruments, packaged in a very small, handheld chassis.