taken, and measurement has at last been commenced. In June two lady assistants were appointed for this purpose, and during the latter half of the year they have measured 62 plates, containing altogether 25,157 stars, each one having been measured in duplicate. In addition, Professor Dyson, Astronomer Royal for Scotland, has very kindly offered to assist in the measurement of the Perth plates. Arrangements have accordingly been made to send him a regular supply of plates and reference star positions from the most southern portion of our region (40°), whilst in Perth a start has already been made from the other end (32°). It has been decided to measure only one image of each star, to duplicate each measurement with plate reversed, to disallow and repeat all measurements which differ in the two positions by 0005 (175) and upwards, and to publish results to three figures only. In justice to Professor Dyson, it should be stated that he wished to take the mean of the two images as was done at Greenwich, and the Director accepts the responsibility of limiting the measurements to the first image only (6 minutes' exposure). He was guided in this decision by Professor Turner's remarks in the Introduction to the Oxford Astrographic Catalogue, vol. i., top of page 25, also page 34, where it is shown that the effect of taking four instead of two measures is to reduce the total probable error of place from ±0" 39 to to"38; and under the present circumstances the extra labour does not appear to be justified. In the determination of the positions of the reference stars practically a new epoch has been inaugurated this year. The observation of the 422 standard stars was completed in March, and a Catalogue giving their positions for 1905'0 was printed and distributed a few months later. This is the first published Catalogue of the Perth Observatory, and it forms the basis of all subsequent work, in the manner therein described. At the end of March reobservation of the reference stars in zone 33°-4°, which had been interrupted for a little over a year by the work of the Standard Catalogue, was renewed upon the fresh basis; that is to say, that instead of determining clock error from Nautical Almanac stars, and N.P.D. from nadir point readings, both clock error and equator point are now determined from the catalogued positions of at least six of the standard stars situated within the zone of observation. The winter was, unfortunately, a phenomenally bad one, by far the cloudiest and most continuously wet that has ever been experienced here. But notwithstanding this, the transit observers made excellent progress, and succeeded in completing the zone 33°-4° on 1908 January 2; and, had there not been an exceptional rush of meteorological work in December, the reductions also would be up to date; as it is, they are only about a fortnight behind. It has been considered advisable to apply corrections to the transit results obtained in previous years (zones 31°-2°, 39°-40°, and the first part of 33°-4°) in order to reduce them to the present adopted standard, viz. that of the first Perth Catalogue. These corrections will be applied before the places are used to determine the plate constants. Considerable progress has been made with zone 39°-40° which is required for Professor Dyson, but it has not been possible to touch the zone 31°-2°, which is required for the plates now being measured here. One piece of astronomical field work was undertaken during the year at the request of the Surveyor-General, viz. the determination of the longitude and latitude of Carnarvon, on the N.W. coast. It may, perhaps, not be out of place to call attention to the results obtained, as the method of observation (almucantar) is only just now coming into favour. The instrument was a 12-inch theodolite by Troughton & Simms. The method of using it was described in Monthly Notices, R.A.S., vol. lxiii. p. 156, with an essential correction in vol. lxiv. p. 70. The weather was very bad. A strong gale was blowing all the time, whirling the sand and dust about, and there was a considerable amount of cloud. An ordinary chronometer was used, without electric attachment. Transits were much interrupted by the following causes:-inability to follow chronometer ticks on account of the wind's howling, clouds, flickering of the light, head being blown away from eyepiece by gusts of wind, sand or insects being blown into observer's eye. Time observations were taken on five nights and latitude on four, with the following results: Diff. of long. 8m. 44806, 44° 12, 44°07, 448'03, 44'03. The results for latitude depend on only three pairs of stars, and for longitude on from six to ten pairs. The following is a résumé of the work during the year: Nights on which time was determined Observations of zone stars in R.A. 197 4240 4240 1230 Separate determinations of (Collimation error II 258 Azimuth error 224 Nadir point 165 71 Readings on meridian mark Meteorological.-As already stated, this department has now been handed over to the Federal Government, but during 1907 the work proceeded as usual. Melbourne Observatory. (Director, Mr. P. Baracchi.) The astronomical work done at this observatory during the year 1907 was as follows:— The list stars were selected from the Melbourne plates of the Astrophotographic Catalogue, to serve as fundamental points of reference for the reduction of these plates. The total number of this class of stars now completely observed not less than three times is 5965. The Annual Catalogue for 1905 has been completed, and the Annual Catalogue for 1906 is nearly ready. The General Catalogue for 1900, including all stars observed since 1894, has been further advanced. Astrophotographic Operations.-The Director regrets to report that the Assistant Observer, Mr. W. J. Wallace, who was connected with this work, died on 28th December last, after a long period of ill-health, which extended over the greater part of the year. The following table shows the number of plates exposed during the year : Chart plates with triple exposure of 30m each Test plates on South Polar regions ... Plates for trails, adjustment of centre, etc. ... Passed as satisfactory. 13 19 4 9 The state of the Astrographic work allotted to this observatory is as follows:: The first series of 1149 plates, covering twice the entire region south of Dec. - 64°, and the series of chart plates with single exposure of one hour, whose centres lie on the parallels of even degrees of declination from 66° to the South Pole, were completed some years ago. A duplicate Catalogue Series is in course, of which 354 regions have been photographed. In the series of chart plates with three exposures of 30m each, having their centres on the parallels of odd degrees of declination, 532 plates have been taken. Thus, the original programme, so far as actual photographic operations are concerned, has been practically carried out. It is intended, however, to complete the second Catalogue Series, and to extend the triple exposure chart plates to the regions of even degrees of declination, as the chart plates with single exposure of one hour are not considered satisfactory. The measurement of plates will be dealt with in a separate report. The following routine duties and other miscellaneous work were carried out for local public requirements as in former years: The Time Service, including daily time signals, control of public clocks, and rating of chronometers for the shipping. The testing of nautical, meteorological, and surveying instruments. The technical operations of the Bureau on Standard Weights and Measures according to law. The Weather Service, including the control of some 1000 reporting country stations. The continuous registration of the variations of sea-level, atmospheric elements, seismic disturbances, and the elements of terrestrial magnetism, including the reduction of magnetic records of past years. An Australian Weather Bureau has been established by the Federal Government with headquarters in Melbourne, but not in any way connected with this observatory. The new institution assumed official control of the weather service of the various States of the Commonwealth on 1st January last, thus relieving the existing Australian observatories of all their public duties in connection with meteorology. Joint Report of the Directors of the Melbourne and Sydney Observatories on the Measurement of the Plates of the Astrophotographic Catalogue.. The Catalogue plates of the Sydney and Melbourne Zones, covering the whole region south of - 51°, are being measured at the Melbourne Observatory by a special Bureau established for this purpose towards the end of 1898, and maintained jointly by the Governments of New South Wales and Victoria. The work of the Bureau during the year 1907 was carried on by a staff of six ladies, under similar conditions, and using chiefly the same pair of Repsold micrometric instruments as in former years. The numbers of plates completely measured in the direct and reversed positions, in the course of the year, are— 138 Sydney plates, containing 97,881 stars. 56 Melbourne plates, containing 15,870 stars. The total aggregate numbers of plates measured up to 31st December 1907 are as follows:— 700 Sydney plates, containing 423,859 stars. 892 Melbourne plates, containing 284,584 stars. Sydney Observatory. (Director, Mr. H. A. Lenehan.) In the early part of the year it was announced that the Government required the site of the observatory for other purposes, and intended to remove the instruments to a new position. In May an Advisory Committee was appointed to act with the Government Astronomer, and many sites suitable for an observatory were inspected. The one finally selected was on or near the Canoblas mountain, in the vicinity of the town of Orange, 130 miles west from Sydney, where there is clearness of definition, freedom from city lights, electrical disturbances, and other troubles which are encountered in the present position of the observatory. Nothing has yet been decided as to the future, and the observatory is still fixed in the original site. The report of the Advisory Committee has not been acted upon. The transit-circle piers and the graduated circles have been cased in, to shield them from air-currents which caused expansion and contraction. This was a very necessary work, and since it has been completed the instrumental corrections have been more constant. There has also been less tarnishing of the graduated silver bands. Other instruments have been in the hands of the mechanician and placed in working order. A 6-inch Grubb equatorial telescope in the north dome required many alterations to make it effective. The alteration of the double pendulum escapement of the cylinder chronograph to a rotary one was much appreciated by the First Assistant. A new direction recording frame has been made for the anemometer. During the year 1908 a new sidereal clock is to be placed in the basement, where it will be free from air-currents and excessive changes of temperature. A 15-inch equatorial telescope is also to be ordered from Sir Howard Grubb. New magnets have been received from Kew Observatory to use at the Red Hill branch, where the magnetic work is carried out. During December three members of the Astronomical Staff left to join the McClean and Lick Observatory parties for solar eclipse observations at Flint Island-two of them joining Mr. McClean. Should fine weather conditions prevail on the eventful day, they will obtain experience that should be of use to them when they are called upon to observe the solar eclipses in Tasmania in 1910 and in Australia in 1911. Mr. Olden has qualified as an observer with the transit-circle, and is of much assistance during the absence of the members of the staff. Improvements have been made in the buildings at the Red Hill branch. A large dark-room has been constructed for the developing of the Astrographic plates, and a new pier erected for the magnet ometer. |