Astronomical Observations Made at Leicester. By the Reverend Mr. Ludlam, Vicar of Norton, Near Leicester. Communicated by the Astronomer Royal

XXXV. Astronomical Observations made at Leicester. By the Reverend Mr. Ludlam, Vicar of Norton, near Leicester. Communicated by the Astronomer Royal. Redde, May 11, 1775. OBSERVATIONS FOR DETERMINING THE LATITUDE OF THE PLACE. Zenith distances taken with an eighteen inch quadrant, made by BIRD. | Year | Degrees | Parts | Degrees | Parts | |------|---------|-------|---------|-------| | | M. S. | S. V. | D. M. S.| P. S. V. | | July | 9 32 | 1 5\(\frac{1}{4}\) | 1 6 40 | 1 1 7\(\frac{3}{4}\) | | | 9 20 | 1 5\(\frac{1}{4}\) | 1 6 34 | 1 1 7\(\frac{1}{2}\) | | | 9 20 | 1 5\(\frac{1}{3}\) | 1 6 34 | 1 1 7\(\frac{1}{2}\) | | | 9 20 | 1 5\(\frac{1}{6}\) | 1 6 28 | 1 1 7\(\frac{1}{4}\) | | | 9 20 | 1 5\(\frac{1}{8}\) | 1 6 27 | 1 1 7\(\frac{1}{2}\) | | Mean | 9 22,4 | 1 5\(\frac{1}{4}\)\(\frac{1}{6}\) | 1 6 32,6 | 1 1 7\(\frac{1}{4}\)\(\frac{1}{8}\) | N.B. The seconds were shewn by the micrometer screw, the fractional parts estimated by the eye. Reduce the parts of 96 to degrees, and take the mean between the zenith distances shewn on each scale, and the zenith distance of β Draconis on the quadrantal arch will be $9^\circ 21',7"$, and on the arch of excess $8^\circ 54"$, whence the true zenith distance is $9^\circ 7',8"$, and the error of the line of collimation $1^\circ 3',8"$, to be subtracted from the numbers shown on the limb of the quadrant. In like manner we shall find the true zenith distance of γ Draconis $1^\circ 6' 19",8"$, and the error of the line of collimation $1^\circ 3',5"$. If we suppose the apparent declination of β Draconis on July 12th to be $52^\circ 28' 52",3"$, that of γ Draconis $51^\circ 31' 41",7"$, we have the latitude from the former $52^\circ 38'$, and from the latter $52^\circ 38' 1"$. N. B. Some observations on these two stars in July 1772, give the same latitude within less than $2"$, but make the error of the line of collimation $23"$ to be subtracted. I suspect the line of collimation is liable to small variations in portable quadrants, if not in all. Zenith distances of $\alpha$ Herculis with the state of the barometer and thermometer. | 1774 | Degrees | Parts of 96 | Barom. | Therm. | |------|---------|-------------|--------|--------| | June | D. M. S. | P. S. V. | Inches | Degrees | | 5° | 37 57 36 | 40 3 14½ | 29,7 | 58 | | July | 2 | 37 57 46 | 40 3 14¾ | 29,8 | 65 | | | 4 | 37 57 40 | 40 3 14½ | 29,7 | 56 | | | 9 | 37 57 41 | 40 3 14¾ | 29,7 | 55 | | | 10 | 37 57 36 | 40 3 14½ | 29,7 | 55 | | | 16 | 37 57 36 | 40 3 14¾ | 30,0 | 65 | | | 18 | 37 57 32 | 40 3 14¾ | 30,0 | 56 | | | 20 | 37 57 32 | 40 3 14¾ | 29,8 | 58 | | Mean | 37 57 37,4 | 40 3 14¾ | 29,8 | 58,5 | The mean of the zenith distances shewn on the two scales of divisions is $37^\circ 57' 32''$. Add for refraction $43,4'$; subtract for line of collimation $13,6'$; and we have the true zenith distance $37^\circ 58' 1,8''$. Suppose the apparent declination of $\alpha$ Herculis on July 12th to be $14^\circ 39' 58'',5'$, we have the latitude $52^\circ 38'$. Zenith distances of the Pole-Star. | Year | Degrees | Parts of 96 | Barom. | Therm. | |------|---------|-------------|--------|--------| | Nov. | D. M. S. | P. S. V. | Inches | Degrees | | 10 | 35° 27' 56" | 37° 6' 9" | 30.05 | 31 | | 11 | 35° 27' 55" | 37° 6' 9" | 29.87 | 32 | | 13 | 35° 27' 56" | 37° 6' 9" | 30.20 | 34 | | Mean | 35° 27' 55.6" | 37° 6' 9" | 30.04 | 32.3 | | Dec. | 6 | 35° 28' 8" | 37° 6' 10" | 30.27 | 30 | | 15 | 35° 28' 4" | 37° 6' 10" | 30.03 | 44 | | Mean | 35° 28' 6" | 37° 6' 10" | 30.15 | 37 | | Dec. | 12 | 39° 15' 0" | 41° 6' 14" | 29.83 | 44 | | 13 | 39° 15' 4" | 41° 6' 15" | 28.86 | 44 | | 15 | 39° 15' 0" | 41° 6' 14" | 30.08 | 38 | | Mean | 39° 15' 1.3" | 41° 6' 14" | 29.59 | 42 | Take the mean between the two scales of divisions, and we have the mean zenith distances, as follows: | Days of the month | Obs. zenith dist. | Cleared of ref. | |------------------|-------------------|-----------------| | Nov. 10 11 13 | D. M. S. | D. M. S. | | | 35° 27' 49.5" | 35° 28' 33.5" | | Dec. 6 15 | 35° 28' 6" | 35° 28' 4" | | Dec. 12 13 15 | 39° 14' 59.3" | 39° 15' 46.7" | The mean zenith distance of Nov. 10, 11, 13, cleared of refraction, is 35° 28' 33.5". To this add 7.5 for the increase of apparent declination between Nov. 12 and Dec. 12, and we have the zenith distance on Dec. 12, (as derived from the observations in November) 35° 28' 41". The same from the actual observations on Dec. 6. and 15. is $35^\circ 28' 44''$. The mean of these two, corrected for the line of collimation, gives the true zenith distance above the pole, $35^\circ 28' 28'',9$. The observations of Dec. 12. 13. 15. cleared of refraction and corrected for the line of collimation, give the true zenith distance below the pole, $39^\circ 15' 33'',1$, whence the latitude $52^\circ 37' 59''$, and the apparent declination of the pole star, Dec. 12th, $88^\circ 6' 27'',9$. From all these observations we may conclude the latitude of (St. Martin's church in) Leicester is $52^\circ 38'$, within very few seconds. From some observations made with an Hadley's quadrant of six inches radius, and given in the Transactions for 1769, I made the latitude only $52^\circ 37' 3''$; but those observations cannot be set in competition with these, either for weight or number. Occultations of $\gamma$ and $\alpha$ Tauri, observed at Leicester, Nov. 18, 1774. | Time by the clock. | H. M. S. | |-------------------|----------| | Emerion $\gamma$ Tauri, | vi 27 10 | | Immersion $\alpha$ Tauri. Touched the limb, | xiv 59 26 | | Vanished, | xiv 59 30 | | Emerion $\alpha$ Tauri instantaneous, | xvi 12 38 | (a) The observations were made in Wigton's hospital adjoining to the church. The following observations serve to examine the clock. Transits of the Sun. | Day of the Month | Time of the Clock | 1st wire | Meridian | 3d wire | |------------------|-------------------|----------|----------|---------| | Nov. 17 | M. S. | H. M. S. | M. S. | | 1774. | 43 35 | xxiii 44 | 45 11½ | | | 45 54 | 46 43 | 47 39 | | 18 | 43 50 | xxiii 44 | 45 26 | | | 46 8½ | 46 57 | 47 44 | Hence the rate of going was conformable to mean time. Zenith distances taken with the eighteen inch quadrant, to ascertain the absolute error of the clock, Nov. 18. Barometer 29.6 inches. Thermometer 33°. | Time by clock | Degrees | Parts of 96 | Object | |---------------|---------|-------------|--------| | H. M. S. | D. M. | P. S. V. | | | viii 0 0 | 67 11½ | 71 5 6 | α Aquilae. | | 2 46 | 67 35½ | 72 0 13½ | | | 12 15 | 68 59 | 73 4 11 | α Aquilae. | | 14 37 | 69 20 | 73 7 10½ | | | 48 4 | 56 45½ | 60 4 5½ | α Tauri. | | 50 55 | 56 20½ | 60 0 13½ | | | 53 23 | 55 59½ | 59 5 13 | | | xi 1 57 | 55 21 | 59 0 5 | | | 3 54 | 55 3 | 58 5 12 | β Geminorum. | | 6 35 | 54 39 | 58 2 5 | | | xvi 26 33 | 58 45½ | 62 5 7 | | | 29 49 | 59 14½ | 63 1 8 | α Tauri. | | 33 9 | 59 44 | 63 5 12 | | | 36 15 | 60 11½ | 64 1 10 | | From... From the mean of the two first zenith distances of α Aquilæ the clock will be found to be slower than mean time 14″. By the second pair of α Aquilæ, 13″. By the next three zenith distances of α Tauri, 13″. By the next three of β Geminorum, 16″. By the last four of α Tauri, 17″; the error of the line of collimation being 13,6 as before. The mean of all these gives the clock 14,6 slower than mean time. Hence, | Solar time. | H. M. S. | |-------------|---------| | Emerion of γ Tauri, | VI 41 48,4 | | Immersion α Tauri. Touched limb, | XV 13 59,6 | | Vanished, | XV 14 3,6 | | Emerion α Tauri, instantaneous, | XVI 27 10,8 | The emersion of α Tauri was observed at Greenwich at XVI 34 36,8 solar time. N. B. The immersion of ξ Tauri (behind the Moon) which was observed at Leicester, April 28, 1770, at IX 45 44 solar time, was also observed at Greenwich at IX 51 28,6 solar time. See Phil. Trans. for 1770. XXXVI. Some