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Rh determined by observing the difference of declination of the upper and lower limb; he adopts the mean diameter 33′. With these data he now calculates the real diameters of the sun and moon, making use of the old value of the solar parallax of 3′, which neither Copernicus nor he thought of discarding. The distance of the sun being 1150 semi-diameters of the earth, the semi-diameter of the sun will be 5.2 times that of the earth, and similarly the distance of the moon is 60 and its semi-diameter 0.29. For the planets he assumes apparent diameters from 2′ to 3′, and calculates from these their diameters and volumes in parts of those of the earth. For the fixed stars Tycho assumes smaller apparent diameters than other astronomers did before the invention of the telescope. With regard to the distance of the stars, he believes the greatest distance of Saturn to be 12,300 semidiameters of the earth (to arrive at which he sketches the theory of Saturn as mentioned above ); and as he does not believe that there is a great void between the orbit of Saturn and the fixed stars, he places these at