This means that the moon will appear to be red like blood. AT: "the moon will appear to be red" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-ellipsis]])
The words "great" and "remarkable" share similar meanings and emphasize the intensity of greatness. AT: "the very great day" (See: [[rc://en/ta/man/translate/figs-doublet]])