Their intensities are on the order of 800 kR near the base, decreasing to about 10 kR near the upper terminus. Blue jets are not aligned with the local magnetic field. Sprites appear to be elusive for several reasons. To see them requires visual access to the region above the storm, unobstructed by intervening clouds, and viewing against a dark stellar background. In most locations these conditions occur only rarely.
Sprites are dim and can only been seen with the dark adapted eye.
On average, their brightness compares to moderately bright aurorae, 10-50 kiloRayleighs. In the human eye, this corresponds approximately to the crossover threshold intensities of cones of the retina, which respond to color, and the somewhat more sensitive but achromatic parfoveal rods, which permit night vision. The dark adapted eye most readily sees sprites in parfoveal vision, when not directly looking at them. Thus, they may quite literally appear only as flashes out of the corner of the eye. Because of their dimness, sprites cannot be viewed in the presence of nearby bright lights, as would be found in a city.