{ "id": "e74f47c107f87b4eafda7d7720107b3eff35ec4e", "text": "XXXII. Observations made at Leicester on the Transit of Venus over the Sun, June 3, 1769. By the Reverend Mr. Ludlam, Vicar of Norton, near Leicester.\n\nRead Nov. 16, 1769.\n\nThe telescope, used for viewing the planet, was made by Mr. Dollond, with a triple object glass of $33\\frac{1}{3}$ inches focal distance, and was found by experiment to magnify 54 times. The clock was firmly fixed; its pendulum rod was made of wood. The transit telescope was not accurately adjusted either to the meridian or horizon, but the transits of the Sun and of $\\eta$ Bootis registered below are sufficient to show the rate of the going of the clock, and the corresponding altitudes of the Sun, its error a few days before the transit of the planet; whence the necessary reduction of the time then shown by the clock to apparent time may be easily derived.\nObservations for examining the clock.\n\n| Day of the month, 1769 | Time by the Clock | Object |\n|-----------------------|------------------|--------|\n| | First Wire | Passage over Meridian | Third Wire |\n| May 28 | | | |\n| | 17 12 | IX 18 0 | 18 47½ |\n| | Clouds | Clouds | Clouds |\n| | | | |\n| | | | |\n| June 1 | | | |\n| | 56 39 | XXIII 57 | 58 17 |\n| | 58 56 | 59 46 | 0 34 |\n\nCorresponding altitudes of the Sun, taken by reflection from water, with an Hadley's quadrant of six inches radius.\n\nSun's double alt. 79° 54' May 29, 1769\n\n| Time by the Clock | Eastern Az. | Western Az. | Meridian |\n|-------------------|-------------|-------------|----------|\n| | h ' \" | | |\n| Up. limb | VIII 28 33 | III 27 39 | XI 58 6 |\n| Center | 30 17½ | 25 51½ | 4½ |\n| Low. limb | 32 8 | 23 57½ | 2¾ |\n| Mean | | | XI 58 4½ |\nSun's double alt. $82^\\circ 55'$\n\n| Time by the Clock | Eastern Az. | Western Az. | Meridian |\n|-------------------|-------------|-------------|----------|\n| Up. limb | h' 11\" | h' 17\" | h' 58\" |\n| Center | 39° | 17° | 58° |\n| Low. limb | 40° | 15° | 4° |\n| Mean | | | |\n| Mean of both sets | | | |\n| Corn for the interv. | | | |\n| Passage over meridian | | | |\n| Equat. of time | | | |\n| Clock faster than mean time | | | |\n\nSun's double alt. $96^\\circ 58'$\n\n| Time by the Clock | Eastern Az. | Western Az. | Meridian |\n|-------------------|-------------|-------------|----------|\n| Up. limb | IX 27 50 | XI 29 44 | XI 58 47 |\n| Center | 29 57 | 27 41 | 49 |\n| Low. limb | 32 1\\(\\frac{1}{2}\\) | 25 36 | 48\\(\\frac{3}{4}\\) |\n| Mean | | | |\n| Corn for interv. | | | |\n| Passage over meridian | | | |\n| Equat. of time | | | |\n| Clock faster than mean time | | | |\n\nIf we suppose the clock to be $1' 11''$ faster than mean time, on June the second at noon, and to gain at the rate of $2\\frac{1}{2}$ seconds in a day, then at the time of the transit of the planet it was one minute and one second slower than apparent time.\n\nAt VII$^h$ 6' 0'', according to the time shewn by the clock, a small indentation appeared on the Sun's limb; the increase of it at VII$^h$ 6' 14'', shewed plainly that it was made by the expected planet.\nThe internal contact was first noted at VII\\textsuperscript{h} 23' 56''; at VII\\textsuperscript{h} 24' 8'', the divided part of the Sun's limb seemed wholly united.\n\nThe edge both of the Sun and Planet were in a continual tremor; at the internal contact the limb of the Sun seemed, for several seconds, to be alternately united and again separated by a kind of shootings of the Planet.\n\nThese observations, reduced to apparent time, give the external contact at VII\\textsuperscript{h} 7' 1'', the internal contact at VII\\textsuperscript{h} 25' 9'', the duration 18' 8''.\n\nThe solar eclipse was observed by the same clock and telescope. It was manifestly begun at XVIII\\textsuperscript{h} 34' 26'', according to the time shewn by the clock. The ending was exactly noted at XX\\textsuperscript{h} 20' 8''. The Sun's limb appeared very well defined all the morning. These observations, reduced to solar time, make the beginning of the eclipse at XVIII\\textsuperscript{h} 35' 21'', the end at XX\\textsuperscript{h} 21' 2'', the duration 1' 45' 41''.\n\nObservations made at Leicester, with an Hadley's quadrant, of six inches radius, for determining the latitude of the place.\n\n| Date | Observation Details | Latitude |\n|------------|-----------------------------------------------------------------------------------|----------|\n| April 27 | Sun's diameter on quadrantal arch | |\n| | on arch of excess | |\n| | repeated on quad. arch | |\n| | on arch of excess | |\n| | Sum of the meridian altitude of the Sun's upper limb, and its depression, when reflected by water | |\n| | of the lower limb | |\n| 29 | Sun's diameter on quadrantal arch | |\n\nApril\n1769 \nApril 29 \nSun's diameter on arch of excess \nrepeated on quadrantal arch \non arch of excess \nMerid. alt. and depression of Sun's upper limb, \nreflected by water \nof the lower limb \nJune 11 \nSun's diameter on quadrantal arch \non arch of excess \nrepeated on quad. arch \non arch of excess \nMerid. alt. and depression of Sun's upper limb, \nreflected by water \nof the lower limb \n15 \nSun's diameter on quad. arch \non arch of excess \nrepeated on quad. arch \non arch of excess \nMerid. alt. and depress. of Sun's upper limb, re- \nflected by water \nof the lower limb\n\nThe latitude of Leicester, deduced from the ob- \nservations of April 27, is \nof April 29, \nof June 11, \nof June 15, \nMean of these four observations\n\nThe latitude of Market Harborough, in Lei- \ncestershire, from the mean of several accurate \nobservations of the Sun's image, projected in- \nto a dark room, by S. 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By the Reverend Mr. Ludlam, Vicar of Norton, Near Leicester", "authors": "Mr. Ludlam", "year": 1769, "volume": "59", "journal": "Philosophical Transactions (1683-1775)", "page_count": 6, "jstor_url": "https://www.jstor.org/stable/105830" } }