Plaskett Report for December 1921

Observing weather though better than November, was very broken as indicated by the relatively few spectrograms obtained. Although observations were made on 17 nights only 109 spectrograms were obtained.

Director J. S. Plaskett obtained 36 spectra on 7 nights. Measured about 20 O-type spectra. Computed wave length tables for the whole range of spectrum on panchromatic plates. Remeasured 10 plates of the eclipsing variable FV Cassiopeiae and computed the orbit. Prepared paper for the JRASC “Temperature Regulation of Spectrograph and Mirror“. Usual administrative and correspondence work.

[This paper is very interesting as it shows Plaskett’s ‘system engineering’ side and his attention to detail. Plaskett understood that to get the best results from a telescope and spectrograph, one had to look at the complete system and address any weaknesses that compromised the final results. In this case, he describes the application of a novel technique to control the temperature of a spectrograph. Interestingly, he was motivated by the time-keepers at the Dominion Observatory, who had used the same equipment to control the temperature of the clocks used to provide Canada’s National. Plaskett was not afraid to borrow techniques from other fields if they would produce better astronomical results. In this paper we also see the effect of World War I as Plaskett notes that the order for the Callendar Recorder was placed in 1916, it wasn’t received until February 1921., Ed.]

Research Astronomer W. E. Harper obtained 39 spectra on 4 nights, Measured 4 for radial velocity and estimated for absolute magnitude 44 spectra. Made survey of 262 A-type stars for type and absolute magnitude. Determined the orbit for one spectroscopic binary and part of another and wrote both for our publications, Volume II, Number 2.

Astronomer R. K. Young obtained 18 spectra on 2 nights for absolute magnitude program. Estimated line intensities on about 1500 plates for determination of absolute magnitude. Computed tables for constants Ao and Bo in Adams’ method of utilizing the parallactic motion for the determination of mean parallax.

Assistant Astronomer H. H. Plaskett obtained 21 low dispersion, 5 high dispersion spectra on 4 nights. Prepared and delivered a lecture on “Super-Helium in the Stars”, which contained account of recent work at the observatory. Prepared and finished a paper for the JRASC on the Pickering Series and Bohr’s Atom. Continued preparation of work on publications, Volume I, Number 30.

[His talk was given on December 14 at the annual meeting of the Victoria Chapter of the Engineering Institute of Canada. John Stanley Plaskett and his wife also attended this meeting and were introdused to the members present. H. H. Plaskett had a lengthy article titled “Vegetation on the Moon” appear in the December 11 edition of the paper., Ed.]

Clerk-Stenographer Miss H. H. Keay handled the usual correspondence and accounts. Filed and catalogued back correspondence in arrears over extra proof reading. Typed two scientific articles and two of the bi-weekly Colonist articles.

Instrument Make Foreman T. T. Hutchison assisted with night observing on 12 nights, opened up on 3 other nights. Installed the heating wires in the temperature case of the spectrograph and rewired and rearranged the circuits for recorder batteries.