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XV. Astronomy Index
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It is possible to find means by which the eye shall not see remote objects as much
diminished as in natural perspective, which diminishes them by reason of the convexity of the eye which necessarily intersects, at its surface, the pyramid of every image conveyed to the eye at a right angle on its spherical surface. But by the method I here teach in the margin [9] these pyramids are intersected at right angles close to the surface of the pupil. The convex pupil of the eye can take in the whole of our hemisphere, while this will show only a single star; but where many small stars transmit their images to the surface of the pupil those stars are extremely small; here only one star is seen but it will be large. And so the moon will be seen larger and its spots of a more defined form 446 . You must place close to the eye a glass filled with the water of which mention is made in number 4 of Book 113 "On natural substances" 447 ; for this water makes objects which are enclosed in balls of crystalline glass appear free from the glass.
Among the smaller objects presented to the pupil of the eye, that which is closest to it, will be least appreciable to the eye. And at the same time, the experiments here made with the power of sight, show that it is not reduced to speck if the &c [32] 448 .
Read in the margin.
[34]Those objects are seen largest which come to the eye at the largest angles.
But the images of the objects conveyed to the pupil of the eye are distributed to the pupil exactly as they are distributed in the air: and the proof of this is in what follows; that when we look at the starry sky, without gazing more fixedly at one star than another, the sky appears all strewn with stars; and their proportions to the eye are the same as in the sky and likewise the spaces between them [61].
141:446 20 and fol.: Telescopes were not in use till a century later. Compare No. 910 and page 136.
141:447 23: libro 113. This is perhaps the number of a book in some library catalogue. But it may refer, on the other hand, to one of the 120 Books mentioned in No. 796. l. 84.
141:448 32: Compare with this the passage in Vol. I, No. 52, written about twenty years earlier.
141:449 : 9. 32. in margine: lines 34-61 are, in the original, written on the margin and above them is the diagram to which Leonardo seems to refer here.
