Astronomical Observations Made in the Austrian Netherlands in 1772 and 1773. By Nathanael Pigott, Esquire, F. R. S. Foreign Member of the Academies of Brussels and Caen. In a Letter to the Reverend Nevil Maskelyne, Astronomer Royal, F. R. S.

XI. Astronomical Observations made in the Austrian Netherlands in 1772 and 1773. By Nathanael Pigott, Esquire, F. R. S. Foreign Member of the Academies of Brussels and Caen. In a Letter to the Reverend Nevil Maskelyne, Astronomer Royal, F. R. S. TO THE REV. NEVIL MASKELYNE. REV. SIR, I RECEIVED, about a month ago, the favour of your letter, and return you many thanks for the Greenwich observations, which you were so obliging to send me. I wait, with impatience, the publication of your journey into Scotland, which must be very curious and interesting. I beg of you, sir, to present my respects to the Royal Society, with the inclosed astronomical observations, which I have contracted as much as I well could, consistently with a view of affording means to verify them, or rectify any mistake which, by inadvertency, may have crept in. I shall only add a short account of the instruments I used, and the elements I employed in the calculations, that a proper judgement may be formed, how far these observations may be depended upon. The meridian altitudes were taken with a quadrant one foot radius made by Mr. Bird, very steadily fixed; free from any communication with the floor, and well placed in the plane of the meridian. Repeated observations for the error of the line of collimation gave $1'58''$, additive to the zenith distances. I always observed both the limbs of the Sun on the meridian, when the weather would permit: its declination was computed from the Nautical Almanac: its parallax and all refractions, account being always kept of the height of the barometer and thermometer, from Professor Mayer's tables, published by the Board of Longitude. The declinations of the fixed stars were taken from the Connoissance des tems. The corrections on account of aberration and nutation, were either taken from the same ephemeris, or computed. My son always observed u's satellites with a reflector, made by Short, of eighteen inches focal length, magnifying 95 times. I observed them with a reflector of two feet and a half focal length, made by Wing, magnifying the diameter of the object about 200 times. The clock was a compound gridiron pendulum, made by the Sieur Le Paute at Paris. The equal altitudes were taken with a quadrant of eighteen inches radius. This astronomical journey was undertaken at the request of the government here. They expressed a desire that the situations of some of their towns, at least, should be determined by observation; and I readily concurred, without regretting either trouble or expense, in a project which had public utility in view. I am, &c. Cor- Corresponding altitude of the Sun and Stars. | Date | Event Description | Altitude | |--------|--------------------------------------------------------|----------| | Aug. 30 | Clock at noon corrected by four obs. of Sun | 11 54 7,9 | | Sept. 5 | Clock at noon corrected by seven ditto | 11 47 26,8 | | | Clock at noon corrected by four ditto | 0 2 48,5 | | | Clock at noon corrected by seven ditto | 11 57 21,1 | | | Clock at noon corrected by seven ditto | 11 54 42,7 | | Oct. 10| Clock at noon corrected by eight ditto | 11 32 37,7 | | | Clock at noon corrected by nine ditto | 11 31 20,2 | | | Clock at noon corrected by five ditto | 11 22 33,1 | | | Clock at noon corrected by five ditto | 11 21 31,0 | | | Clock at noon corrected by six ditto | 11 20 30,5 | | Nov. 9 | Clock at noon corrected by five ditto | 0 21 23,6 | | | Clock at noon corrected by three ditto | 0 23 10,4 | | | Clock at noon corrected by three sets ditto | 0 24 55,1 | | | Clock at noon corrected by six ditto | 0 25 9,7 | | | Clock at noon corrected by seven ditto | 0 30 30,5 | | | Ditto. Fomahant crossed the meridian by the clock | 7 28 28,0 | | | Ditto. Fomahant crossed the meridian by ditto | 7 25 19,9 | | Dec. 23| β Ceti on meridian by the clock | 6 39 38,5 | | | Clock at noon corrected by four obs. of Sun | 0 19 6,9 | NAMUR NAMUR 1772. By a mean of eight meridian altitudes of the fixed stars taken in September, I determined the latitude of my observatory, in the Rue St. Nicholas, near the Recollets Church, $50^\circ 28' 32''$ North. Sept. 4, emersion of $\pi$'s first sat. at $10^h 38'$ by the clock. | Apparent times. | h | ' | " | |-----------------|---|---|---| | Emersion at Tyrnaw in Hungary, by Father Weiss, 3$\frac{1}{2}$ feet achrom. | 11 | 41 | 11 | | To reduce to time of the Royal Observatory at Paris, | -1 | 0 | 55 | | Emersion of the sat. at Paris, | 10 | 40 | 16 | | Emersion by my son at Namur, | 11 | 49 | 55 | | Namur East of the Paris Observatory, in time, | 9 | 39 | Or in parts of a great circle $2^\circ 24' 45''$. A very good observation. $\pi$'s belts very distinct. I saw the emersion $5''$ latter. By a mean of twenty-nine meridian altitudes of the Sun and fixed stars taken in September and October, one of which only, gives the latitude $19^\circ 9''$ different from the mean of the whole, I determined the latitude of my observatory, in the Rue St. Esprit, near the Jesuits Church, $49^\circ 37' 6'' +$ North, Sept. 11. emersion $24'$s first sat. $12^h 55' 20''$ by the clock. | Apparent times. | h | ' | " | |-----------------|---|---|---| | Emersion at Greenwich, by the Nautical Almanac, | 12 | 28 | 15 | | Error of tables, by a good observation at Tyrnaw, Sept. 4, | +0 | 7 | | Greenwich West of Paris, | +9 | 16 | | Emersion at Paris, | 12 | 37 | 38 | | I observed it at Luxembourg, | 12 | 53 | 19 | | Luxembourg East of Paris Observatory, | 15 | 41 | My son saw the emersion $19''$ later. LUXEMBOURG, Sept. 20, 1772. Emerion u's first sat. at 9h 15' 23" by the clock. Apparent times. | Description | h | m | s | |--------------------------------------------------|-----|-----|-----| | Emerion at Greenwich, by Nautical Almanac | 8 | 55 | 12 | | Error of tables, as above | | + | 7 | | Greenwich West of Paris | | + | 9 | 16 | | Emerion at Paris | 9 | 4 | 35 | | I observed it at Luxembourg | 9 | 19 | 52 | | Luxembourg East of Paris | | | 15 | 17 | My son observed the emersion 13" later. The same emersion. | Description | h | m | s | |--------------------------------------------------|-----|-----|-----| | Emerion at Greenwich, by Nautical Almanac | 8 | 55 | 12 | | Error of tables, by an observation at Greenwich on the 27th | - | 25 | | At Greenwich, by the tables corrected | 8 | 54 | 47 | | Difference of meridians | | + | 9 | 16 | | Emerion at Paris | 9 | 4 | 3 | | I observed it at Luxembourg | 9 | 19 | 52 | | Luxembourg East of Paris | | | 15 | 49 | Mr. Pigott's Astronomical Observations LUXEMBOURG, Oct. 19, 1772. Emersion 4° second sat. at 7h 31' 39" by the clock. Apparent time. | Location | Time | |---------------------------|----------| | Emersion at Tyrnaw, achrom. | 8 54 47 | | To reduce to Paris time | -1 0 55 | | At Paris | 7 53 52 | | My son observed it at Luxembourg | 8 9 14 | | Luxembourg East of Paris | 15 22 | I saw it 3" later. The same emersion. At Senones, by M. Messier, achrom. 5 feet, 8 12 8 To reduce to Paris time, according to his letter, -18 34 Emersion at Paris, 7 53 34 At Luxembourg, 8 9 14 Luxembourg East of Paris, 15 40 This emersion was observed also at 7h 44' 13" apparent time, with a 6 feet reflector, at Greenwich. Allowing, according to the Astronomer Royal's rule, about 20" for the difference of telescopes, the result will be, Luxembourg East of Paris 15' 25". LUXEMBOURG, Oct. 20, 1772. Emersion 4's first sat. at 11h 0' 15" by the clock. Apparent time: | | h | m | s | |----------------|-----|-----|-----| | Emersion at Greenwich, achrom. 3½ feet, | 11 | 14 | 18 | | To reduce to Paris time, | + | 9 | 16 | | At Paris, | | | | | I observed it at Luxembourg, | 11 | 23 | 34 | | Luxembourg East of Paris, | 11 | 39 | 13 | My son saw it 12" later. **Mr. Pigott's Astronomical Observations.** **LUXEMBOURG, Oct. II, 1772.** **Eclipse of the Moon.** | By clock | Appar. time | Luxemb. East of Paris | |----------|-------------|-----------------------| | | | | | 6 25 | 18 6 54 17 | Galileus out of the shadow at Luxembourg, | | 6 36 | 5 7 5 4 | Copernicus begins to emerge at Luxembourg, | | 6 38 | 7 6 59 | Copernicus out at Luxembourg, | | | 6 51 37 | at Senones, reduced to Paris, | | | 6 51 54 | at the Observatory at Paris, | | 6 40 | 42 7 9 41 | Tycho begins to emerge at Luxembourg, | | 6 42 | 35 7 11 34 | Tycho out at Luxembourg, | | | 6 56 13 | at Senones, reduced to Paris, | | | 6 55 56 | at the Observatory at Paris, | | | 6 56 21 | Rue St. Honore at Paris, by M. de la Lande, | | 6 53 | 56 7 22 54 | Manilius begins to emerge at Luxembourg, | | | 7 7 25 | at the Observatory at Paris, | | | 7 7 28 | Paris, Rue St. Honore, | | 7 3 | 25 7 32 25 | Mare Serenitatis out at Luxembourg, | | | 7 17 10 | Senones, reduced to Paris, | | | 7 17 23 | at the Observatory at Paris, | | 7 12 | 17 7 41 17 | Mare Crisium begins to emerge at Luxembourg, | | | 7 26 18 | at Paris, Rue St. Honore, | | 7 17 | 37 7 46 35 | Mare Crisium out at Luxembourg, | | | 7 30 45 | at Senones, reduced to Paris, | By a mean, | 7 52 | 7 end of the eclipse at Luxembourg. | | 7 33 | 55 at Senones, by M. Messier, reduced to Paris. | | 7 35 | 46 at the Royal Observatory at Paris. | | 7 34 | 54 Paris, Rue St. Honore, by M. de la Lande. | At Luxembourg, Sky remarkably clear, without the least wind. Hence, by a mean of 24's satellites, Luxembourg East of the R. Observ. at Paris, by a mean of the whole, Which gives $3^\circ 51' 45''$ in parts of a great circle. **LUXEM-** LUXEMBOURG, 1772. Oct. 22. at 3 hours P. M. a magnetic needle of four inches, made by DOLLOND, gave the declination West $18^\circ 42' \frac{1}{2}$. Oct. 23. at 10 hours A. M. the declination was $18^\circ 50'$. At LA HEESSE, near HOOGSTRAETEN. By a mean of twenty-two meridian altitudes of the Sun and fixed stars taken in November 1772, one of which only, gives the latitude different from the mean of the whole $10''$, I determined the latitude of my observatory $51^\circ 23' 2'' + N$. Nov. 9. Emerision 4's third sat. 6h 49' 29'' by the clock. | Apparent time. | h | ' | " | |----------------|---|---|---| | Emerision at Tyranaw, achrom. 3\(\frac{1}{2}\) feet, | 7 | 19 | 2 | | To reduce to Paris time, | -1 | 0 | 55 | | Emerision at Paris, | 6 | 18 | 7 | | I observed it at La Heese, | 6 | 27 | 50 | | La Heese East of the Paris Observatory, | 9 | 43 | My son saw the Emerision 1.3'' later. Mr. PIGOTT's Astronomical Observations. LA HESE, Nov. 14, 1772. Emersion u's first sat. at 6h 44' 5" by the clock. | Apparent time. | |----------------| | h ' " | Emersion at Senones, achrom. 3½ feet, To reduce to Paris time, Emersion at Paris, I observed it at La Heese, La Heese East of Paris, The same emersion. At Greenwich, 6 feet reflector, Difference of telescopes, Greenwich West of Paris, Emersion at Paris, By my observation at La Heese, La Heese East of Paris, Nov. 20. Emersion u's second sat. at 8h 15' 59" by the clock. Emersion by my son, but I have no corresponding observation, At La Heese, Nov. 21, 1772. Emersion u's first sat. at 8h 45' 12" by the clock. | Apparent time. | |----------------| | h ' " | Emerion at Greenwich, by Nautical Almanac, 7 53 54 Error of tables, by the observ. at Greenwich, Senones, and Tyrnaw, + 12 Greenwich West of Paris, + 9 16 Emerion at Paris, 8 3 22 I observed it at La Heese, 8 13 5 La Heese East of Paris, 9 41 My son saw the emersion 5" later. By a mean of the observations of u's satellites, La Heese is East of the Royal Observatory at Paris 9' 49" in time, or 2° 27' 15". If the observation of Nov. 14, compared with that made at Senones, be rejected, the difference of meridians will be 7½ in time less. At Hoogstraeten, Nov. 24, 1772. By a base of 3028 feet, twice very exactly measured and angles taken with a quadrant 18 inches radius, I determined the church of Hoogstraeten 10380 feet North and 5873 feet East of the Observatory at La Heese. Hence latitude of La Heese, $51^\circ 23' 2'' +$ Difference of latitudes, $+ 1' 42''$ Latitude North of the church of Hoogstraeten, $51^\circ 24' 44''$ Longitude of La Heese, as above, $9^\circ 49'$ Difference of meridians, $+ 6'$ Hoogstraeten East of the Royal Observatory at Paris, in time, $9^\circ 55'$ Or $2^\circ 28' 45''$ in parts of a great circle. At Ostende. By a mean of 24 meridian altitudes of the Sun and stars taken in December, one of which only, gives the latitude $11', 7''$ different from the mean of the whole, I determined the latitude of my observatory, in the Rue de la Poste $51^\circ 15' 10''$ North. The Connoissance des tems gives the lat. $51^\circ 13' 55''$; but I do not know in what part of the town, or by whom it was determined. At At Ostende, Dec. 23, 1772. Emersion u's first sat. at 4h 52' 48" by the clock. | Apparent time. | |---------------| | h ' " | | 4 22 1 | | + 12 | | + 9 16 | Emersion at Greenwich, by Nautical Almanac, Error of tables, as Nov. 21, Greenwich West of Paris, Emersion at Paris, I observed it at Ostende, Ostende East of Paris Observatory, in time, Or 38' 15" in parts of a great circle. Twilight strong; sky very clear and serene; good observation. Dec. 24, at 3 hours P. M. I found the declination of the magnetic needle West 20° 35'½. At Tournai, 1773. By a mean of 14 meridian altitudes of the Sun and stars taken in January, one of which only gives the latitude 22",8 different from the mean of the whole, I determined the latitude of my observatory in the Rue des Jésuites 50° 36' 57"+ North. The weather would not permit to observe either u's satellites, or an occultation of a star by the Moon, for the longitude of Tournai.