In like manner it may thus appear through the visual organ, that is, the eye, which on account of some infirmity, or because of fatigue, is changed into some degree of dimness or into some degree of weakness.
So it happens very often, owing to the membrane of the pupil becoming suffused with blood, on account of some corruption produced by weakness, that things all appear of a red colour; and therefore the star appears so coloured.

And owing to the sight being weakened, there results in it some dispersion of the spirit, so that things do not appear united, but scattered, almost in the same way as our writing does on a wet piece of paper.

And this is the reason why many persons, when they wish to read, remove the paper to some distance from the eyes, in order that the image thereof may come within the eye more easily and more subtly, and thereby the lettering is left impressed on the sight more distinctly and connectedly.

For like reason the star also may appear blurred; and I had experience of this in the same year in which this Song was born, for, by trying the eyes very much in the labour of reading, the visual spirits were so weakened that the stars all appeared to me to be blurred by some white mist: and by means of long repose in shady and cool places, and by cooling the ball of the eye with spring water, I re-united the scattered powers, which I restored to their former good condition.
And thus, for the reasons mentioned above, there are many visible causes why the star can appear to us different to what it really is..