1,339. More Visible in the Winter

Hilchos Kiddush HaChodesh 18:2

The visibility of the moon will be greater on a clear day in the winter than it is in the summer. This is because on a clear winter day the air is clearer and the skies are brighter thanks to an absence of dust in the air. In the summer, the air is smokey because of all the dust, which makes the moon look smaller.

Hilchos Kiddush HaChodesh 18:3

When the arc of visibility and the first longitude are low, the moon will appear smaller so it will only be visible from a very high altitude. If the arc of visibility and the first longitude are higher, with degrees added, then the moon will appear larger. The moon’s size and the extent to which it can be seen increase as the arc of visibility and the first longitude increase.