Why should an astronomer write a commentary on the Bible?

Because commentators as a rule are not astronomers, and therefore either pass over the astronomical allusions of Scripture in silence, or else annotate them in a way which, from a scientific point of view, leaves much to be desired.

Astronomical allusions in the Bible, direct and indirect, are not few in number, and, in order to bring out their full significance, need to be treated astronomically. Astronomy further gives us the power of placing ourselves to some degree in the position of the patriarchs and prophets of old. We know that the same sun and moon, stars and planets, shine upon us as shone upon Abraham and Moses, David and Isaiah. We can, if we will, see the unchanging heavens with their eyes, and understand their attitude towards them.