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

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. Read Nov. 16, 1769. The 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. Observations for examining the clock. | Day of the month, 1769 | Time by the Clock | Object | |-----------------------|------------------|--------| | | First Wire | Passage over Meridian | Third Wire | | May 28 | | | | | | 17 12 | IX 18 0 | 18 47½ | | | Clouds | Clouds | Clouds | | | | | | | | | | | | June 1 | | | | | | 56 39 | XXIII 57 | 58 17 | | | 58 56 | 59 46 | 0 34 | Corresponding altitudes of the Sun, taken by reflection from water, with an Hadley's quadrant of six inches radius. Sun's double alt. 79° 54' May 29, 1769 | Time by the Clock | Eastern Az. | Western Az. | Meridian | |-------------------|-------------|-------------|----------| | | h ' " | | | | Up. limb | VIII 28 33 | III 27 39 | XI 58 6 | | Center | 30 17½ | 25 51½ | 4½ | | Low. limb | 32 8 | 23 57½ | 2¾ | | Mean | | | XI 58 4½ | Sun's double alt. $82^\circ 55'$ | Time by the Clock | Eastern Az. | Western Az. | Meridian | |-------------------|-------------|-------------|----------| | Up. limb | h' 11" | h' 17" | h' 58" | | Center | 39° | 17° | 58° | | Low. limb | 40° | 15° | 4° | | Mean | | | | | Mean of both sets | | | | | Corn for the interv. | | | | | Passage over meridian | | | | | Equat. of time | | | | | Clock faster than mean time | | | | Sun's double alt. $96^\circ 58'$ | Time by the Clock | Eastern Az. | Western Az. | Meridian | |-------------------|-------------|-------------|----------| | Up. limb | IX 27 50 | XI 29 44 | XI 58 47 | | Center | 29 57 | 27 41 | 49 | | Low. limb | 32 1\(\frac{1}{2}\) | 25 36 | 48\(\frac{3}{4}\) | | Mean | | | | | Corn for interv. | | | | | Passage over meridian | | | | | Equat. of time | | | | | Clock faster than mean time | | | | If 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. At 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. The 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. The 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. These 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''. The 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''. Observations made at Leicester, with an Hadley's quadrant, of six inches radius, for determining the latitude of the place. | Date | Observation Details | Latitude | |------------|-----------------------------------------------------------------------------------|----------| | April 27 | Sun's diameter on quadrantal arch | | | | on arch of excess | | | | repeated on quad. arch | | | | on arch of excess | | | | Sum of the meridian altitude of the Sun's upper limb, and its depression, when reflected by water | | | | of the lower limb | | | 29 | Sun's diameter on quadrantal arch | | April 1769 April 29 Sun's diameter on arch of excess repeated on quadrantal arch on arch of excess Merid. alt. and depression of Sun's upper limb, reflected by water of the lower limb June 11 Sun's diameter on quadrantal arch on arch of excess repeated on quad. arch on arch of excess Merid. alt. and depression of Sun's upper limb, reflected by water of the lower limb 15 Sun's diameter on quad. arch on arch of excess repeated on quad. arch on arch of excess Merid. alt. and depress. of Sun's upper limb, re- flected by water of the lower limb The latitude of Leicester, deduced from the ob- servations of April 27, is of April 29, of June 11, of June 15, Mean of these four observations The latitude of Market Harborough, in Lei- cestershire, from the mean of several accurate observations of the Sun's image, projected in- to a dark room, by S. Rouse