Great is our Lord - See the notes at Psalms 48:1.
And of great power - This seems to be added, as in Isaiah 40:28, in view of the power required in making the heavens, and in guiding and numbering the stars: “Hast thou not known? Hast thou not heard, that the everlasting God, the Lord, the Creator of the ends of the earth, fainteth not, neither is weary?”
His understanding is infinite - Margin, Of his understanding there is no number. That is, This corresponds with his power to number the stars. There is no limit to it. It is not bounded; there is no point reached where it can be said that there is no more; that it is exhausted. See the notes at Isaiah 40:28 : “There is no searching of his understanding.”