E 4
The tabulation of its records has been done independently by two observers, the hourly values thus found usually agreeing to within one mile in ordinary winds: In high and squally winds the record is admittedly not easy to evaluate and the differences are occasionally larger, but it is not thought that any serious error has arisen from this source.
*
Some details of the comparison of the two instruments will be found in Tables XI and XII published in "Meteorological Observations 1910"
17. In view of the possibility of Halley's Comet being visible during its transit of the Sun on May 19th, a camera from which the lens had been removed was fitted to the Lee Equatorial, and adjusted so that a photographic plate was situated in the principal focus of the six inch object glass. The computed time of ingress and egress, 11 hours 6 minutes and 12 hours 6 minutes Hongkong Mean Time, kindly communicated by Kiel, was received by telegram early in the morning.
The sky was partially clouded but during breaks our exposures were made between 10h. 9m. and 10h. 25m., and during transit nine exposures between 11h. 21m. and 12h. 5m., after which the sky became entirely overcast. The plates were successfully developed by Mr. Jeffries. The sun's disc had a diameter, on the plates, of one inch only, but under magnification a fair amount of detail could be detected in a group of spots situated near its centre. A critical examination of the negatives, however, revealed no trace of the comet.
The comet was first seen by the naked eye on April 17th, when it appeared to be of about the fourth magnitude. It was last so seen on June 25th, when it could scarcely have been picked up without an accurate knowledge of its position. In the meantime towards the middle of May, it had presented a most brilliant spectacle.
18. In 1910 the number of transits observed was 510. The axis of the transit instrument was levelled 279 times, and the azimuth and collimation errors were determined 24 times by aid of the meridian mark. The whole of these observations have been made by Mr. Plummer. No alterations have been made to any of the standard clocks during the year and the going of them all has been entirely satisfactory.
19. The errors of the Time Ball are given on Table I. The ball is not dropped on Sundays nor on Government holidays. There was one failure, on February 16th, in consequence of the ball becoming jammed near the top of the mast. It was afterwards discovered that the ball had become separated from the hoisting gear and the necessary repairs were not completed until March 1st. On June 30th the ball was not dropped owing to a typhoon to the Westward of Hongkong, and again on August 31st, when there was a typhoon in the neighbourhood of Gap Rock. It was dropped
E 4
The tabulation of its records has been done independently by two observers, the hourly values thus found usually agreeing to within one mile in ordinary winds: In high and squally winds the record is admittedly not easy to evaluate and the differences are occasionally larger, but it is not thought that any serious error has arisen from this source.
*
Some details of the comparison of the two instruments will be found in Tables XI and XII published in "Meteorological Observa- tions 1910"
17. In view of the possibility of Halley's Comet being visible during its transit of the Sun on May 19th, a camera from which the lens had been removed was fitted to the Lee Equatorial, and adjusted so that a photographic plate was situated in the principal focus of the six inch object glass. The computed time of ingress and egress, 11 hours 6 minutes and 12 hours 6 minutes Hongkong Mean Time, kindly communicated by Kiel, was received by telegram early in the morning.
The sky was partially clouded but during breaks our exposures were made between 10h. 9m. and 10h. 25m., and during transit nine exposures between 11h. 21m. and 12h. 5m., after which the sky be- came entirely overcast. The plates were successfully developed by Mr. Jeffries. The sun's disc had a diameter, on the plates, of one inch only, but under magnification a fair amount of detail could be detected in a group of spots situated near its centre. A critical examination of the negatives, however, revealed no trace of the comet.
The comet was first seen by the naked eye on April 17th, when it appeared to be of about the fourth magnitude. It was last so seen on June 25th, when it could scarcely have been picked up without an accurate knowledge of its position. In the meantime towards the middle of May. it had presented a most brilliant spectacle.
18. In 1910 the number of transits observed was 510. The axis of the transit instrument was levelled 279 times, and the azimuth and collimation errors were determined 24 times by aid of the meridian mark. The whole of these observations have been made by Mr. Plummer. No alterations have been made to any of the standard clocks during the year and the going of them all has been entirely satisfactory.
19. The errors of the Time Ball are given on Table I. The ball is not dropped on Sundays nor on Government holidays. There was one failure, on February 16th, in consequence of the ball be- coming jammed near the top of the mast. It was afterwards dis- covered that the ball had become separated from the hoisting gear and the necessary repairs were not completed until March 1st. On June 30th the ball was not dropped owing to a typhoon to the West- ward of Hongkong, and again on August 31st, when there was a typhoon in the neighbourhood of Gap Rock. It was dropped
No comments yet.
Private notes are available after approval.