The 818-MSCOPE is a Microscope Slide power sensor that measures the optical power at the sample plane in a microscopy setup. The silicon photodiode measures from 350 to 1100 nm at optical powers ranging from 3µW to 1W and is designed to be a microscopy power sensor that answers the needs of fluorescence excitation measurements. The sensor has a footprint of 76.0 mm x 25.2 mm matching that of a standard microscope slide. The sensing area is protected and cleanable sealed so that it can measure with in an immersion medium such as water or glycerol as well as in air. The sensor has a 1.5 meter long cable for connecting to a meter or PC interface.