a cover having a transparent body having an outer surface, an inner surface, an apex and a wall, the wall not having any flat portion and depending down from the apex to terminate at a lower edge in an open periphery, the body being formed with a first pair of opposed converging faces, the body being formed between the apex and periphery with a second pair of opposed converging faces, the first pair being closer to the apex than the second pair, each pair being parallel to the open periphery, the first pair having faces of approximately equal length, the second pair having a short face and a long face; and a skylight tube coupled to the cover.