Complex sentence: For the halo to form the sun must be very high in the sky, at an elevation of 58 ° or more and cirrus cloud or haze containing relatively large plate-shaped ice crystals must be present.
Split into simpler sentences: For the halo to form the sun must be very high in the sky, at an elevation of 58 ° or more. Cirrus cloud or haze containing relatively large plate-shaped ice crystals must also be present.