PROBLEM XXXIII.

22

00 00

17 55 4

4 4

56

10

6 34 2

To direct the line of sight to any star or planet.

Adjust the instrument; that is, place it so that the

circles of altitude and declination may be in the plane

of the meridian set the semicircle of altitude to the co-latitude, and the circle of declination of the given body.

Take the difference between the right ascension of the sun and given body, and if the right ascension of the body be greater than that of the sun, subtract the difference; if not, add to the time of observation. The remainder in one case, or the sum in the other will be the hour and minute to which the nonius on the horary circle is to be set; which being done, the sight will point to the star or planet sought.

If the time be too small to admit of having the dif ference taken from it, borrow 24 hours, and reckon the remainder from XII at noon.

PROBLEM XXXIV. To find the longitude.*

Adjust the instrument to the co-latitude and meridian, and take the time of the transit of the moon's limb, and also of a proper star, as near as possible to the moon's parallel, and the longitude may be deter mined by the following rule.

Rule. Find from the Nautical Ephemeris, the increase of the moon's right ascension in 12 hours; observe, as before directed, the interval of time between the passage of a given fixed star, and of the moon's enlightened limb, over the meridian at each place, and the difference of these intervals will shew the increase of the moon's right ascension in the time of the star's passage from one * Vinee's Practical Astronomy, p. 90 and 169.

meridian to the other. But as the increase of the moon's R. A. in 12 hours is to 180°, so is the above difference of intervals, to the difference of longitude.

Example, on Nov. 30, 1792.

13h 12' 57.62" meridian transit of the

moon's 2d limb

13 13 29.08 meridian transit of a m

at Greenwich,

Sby the clock

9.38 increase of moon's right ascension between Greenwich and York by observation, which reduced into degrees gives 141". Now the increase of the moon's right ascension in twelve hours was 23340"; hence as 23340" to 180°, so is 141" to 1°5' 14′′, the difference of longitude between Greenwich and York.

Those stars that are nearest in right ascension and declination to the moon, are best suited for this purpose.

Table of the Elliptic Motions of the Planets, as given by La Place in his System du Monde, Troisieme Edition, 1808.

Jupiter..0-04817840+0-000159350 Georgium Sidus 0 46 26..+3 13

Table of the Four New Planets, from the Same.