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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1766 Excerpt: ...directly through the upper hole of the vane, and holding the plane of the quadrant so as to pass through the sun and moon, vibrate it a little, for the more certainty of its being sometimes in the proper plane, and move the index from (0) till the sun's image appears; then bring the nearest limbs of the sun's image and moon to coincide, vibrating the quadrant about the axis of vision to make the sun's image pass by the moon, that the contact may be more accurately determined. Then read off their distance, and correct it (if necessary) for the error of adjustment, and add the sum of their semidiameters, found from the nautical almanac as before directed, and it gives the apparent distance of the centers of the sun and moon. 47. To find the moons apparent difiance from a fiar. The mode of operation is the fame for this as for the last case, only you must look at the star directly, and bringing up the enlightened limb of the moon's image to it, vibrate the quadrant until the image, when it passes by the star, cuts it in the middle (for the F star star sometimes appears of a sensible diameter). If the nearest limb of the moon be brought up to the star, the semidiameter of the moon must be added to the angle shown by the index, corrected (if necessary) for the error of adjustment, and it gives the apparent distance of the moon's center from the star; but if the furthest limb be brought up (in which case the moon's image must be made to pass over the star), the semidiameter must be subtracted.--If a telescope be used which inverts, the moon's image will appear to approach the star in an opposite direction; therefore the observer must be caresul not to mistake and suppose the image is beyond the star when it is not up to it. 48. to observe corresponding or equal a...

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