Complex sentence: During Winter, in December, for example, the lens had to be lowered by four inches, compared to its position in June as the position of the sun in the sky is lower in winter than during the summer.
Split into simpler sentences: During Winter, in December, for example, the lens had to be lowered by four inches, compared to its position in June. This is due to the fact that during the winter the position of the sun in the sky is lower than during the summer.