Pagina-afbeeldingen
PDF
ePub
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

M pNov. 4

[ocr errors]

S

[ocr errors]

1855 M t May 2 4 M1870 Mt Jan. 17

May 16 21 M

Mt Oct. 25 8

[1856M p/April 20 91 M1871 M_p[Jan. 6

M pJuly 23
Aug. 7

A

[blocks in formation]

Mt July 12

11 A

M

IS Dec 22

03 A

91 A

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][ocr errors][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors][merged small]

Though the preceding table be calculated only for nineteen years, it will answer for a century to come, by changing the years at the expiration of nineteen; thus, instead of 1805, write 1824, and so on in a gradual succession to 1842, without any alteration in the figures under the months; and when these years are elapsed, begin again with 1843, &c.

To find the time of new moon, subtract the number in the table opposite to the given year, and under the given month, from 30.

Examples. The time of new moon in March 1820, is on the 14th, (-30--16;) in December the same year, new moon happens on the 5th (=30-25 ;) and so on for any other year and month.

To find the time of full moon, subtract the number in the table opposite to the given year, and under the given month, from 30; if the remainder be 15, full moon happens on the 30th day of the month; if the remainder exceed 15, the excess above 15 is the day of the month on which full moon happens; if the remainder fall short of 15, add 15 to it, and the sun will show the day of the month on which full moon will happen.

Examples. Full moon happens on January 30, 1820, (50-15-15.) In November, 1818, full moon happens on the 12 (30—3—27, and 2715=12.) In January, 1818, full moon happens on the 23 (30—23—7, and7+15-22.)

At the time of conjunction, or new moon, the sun and moon are in the same sign and degree, and the moon's motion is 12° 11' 6" swifter than the apparent motion of the sun (see the note page 74 ;) if this difference, therefore, be multiplied by the moon's age, the product will give the number of degrees which the moon's place is before the sun's; and, as the sun's place is readily found by the globe, the moon's place will be easily obtained. Likewise, if the place of the moon's node* be given for any particular year, its place for any other year may be calculated, the mean annual variation being about 19° 19′ 44′′ (see page 133.) Hence, the following problem may be solved, though not very accurately, without an ephemeris.

* In a central eclipse of the moon, the moon's place at the middle of the eclipse is directly opposite to the sun, and the moon is then in one of her nodes. If the sun's place in the ecliptic be determined at that time by observation, the opposite point will be the true place of the moon's node.

246

PROBLEM LV.

To find the time of the year when the sun or moon will be liable to be eclipsed.

Rule. 1. Find the place of the moon's nodes, the time of new moon, and the sun's longitude at that time, by an ephemeris ;* then, if the sun be within 17 degrees of the moon's node, there will be an eclipse of the

sun.

2. Find the place of the moon's nodes, the time of full moon, and the sun's longitude at that time, by an ephemeris; then, if the sun's longitude be within 12 degrees of the moon's node, there will be an eclipse of

the moon.

Examples. 1. On the 15th of January, 1805, there was a full moon, at which time the place of the moon's node was 25° 54', and the sun's longitude 25°; did an eclipse of the moon happen at that time?

Answer. Here the sun was nearly in the moon's node, therefore, a total eclipse of the moon took place; for, when the sun is in one of the moon's nodes at the time of full moon, the moon is in the other node, and the earth is directly between them; the moon's place was consequently about 25° in Cancer.

2. It appears by the foregoing table, that there was a new moon on the 30th of January, 1805, at which time the place of the moon's node was 25° 16′, and the sua's longitude or place was 10°; was there an eclipse of the sun at that time?

3. By the foregoing table, or by an ephemeris, there was a new moon on the 19th of October, 1808, at which time the place of the moon's node was m. 13° 6', and the sun's longitude ± 25° 56′; was there an eclipse of the sun at that time?

4. On the 3d of November, 1808, there was a full moon, at which time the place of the moon's node wasm 12° 18′, and the sun's longitude m. 10° 55'; was there an eclipse of the moon at that time?

5. Ôn the 4th of April, 1810, there was a new moon, at which time the place of the moon's node was 14°

* White's Ephemeris, or the Nautical Almanac.

« VorigeDoorgaan »