Altostratus forms a widespread grey or blue-grey sheet. Thinner parts can reveal the Sun as a blurred patch, like a light behind frosted glass. Unlike cirrostratus, the layer itself does not produce halos.
Choose the overall sheet before getting distracted by small details. This photograph has pouch-like features underneath an altostratus layer; not every example is featureless. It is a useful bridge between a translucent veil and a thick rain-bearing sky. Compare texture and transparency, and leave uncertain cases unnamed.
Photo: GerritR · CC BY-SA 4.0. Resized and recompressed; image retains its source license.
