Abstract
STELLAR PHOTOMETRY.—Mr. Chandler, of Cambridge, U.S., presented an interesting and important paper to the Section of Mathematics and Astronomy of the American Association at the recent meeting, the title being “A Comparative Estimate of Methods and Results in Stellar Photometry.” According to the account of the paper given in Science (vol. viii., No. 187), Mr. Chandler took for his text the general statement that instrumental photometry had thus far proved a failure; that is, it had not developed a more uniform scale than Argelander's, nor had the accuracy of individual determinations been increased, but they were, on the contrary, far more uncertain than the old differential naked-eye estimates. In support of his views Mr. Chandler showed that, for stars of Argelander's scale between magnitudes 2 and 6, the photometric catalogues of Seidel,. Peirce, Wolf, Pickering, and Pritchard differed among themselves as much in their measures of what Argelander called a difference of one magnitude, as they did in their measures of his successive magnitudes. Their average values of the logarithm of the light-ratio for one of Argelander's magnitudes between 2 and 6, ranged between.30 and.38, about.35 for the mean of all the above-mentioned catalogues. Between magnitudes 6 and 9 of Argelander's scale, the catalogues of Rosén and Ceraski averaged about.35 for the light-ratio, while Pickering's late results with the meridian photometer gave (between magnitudes 6 and 8.5).48 instead of.35 for this ratio. Coming to accidental errors, Mr. Chandler showed that, from a discussion of the naked-eye estimates of Gould, Sawyer, and himself, the probable error of a single estimate was a little over ±.06 of a magnitude when the stars were at considerable distances from each other, and about ±.05 of a magnitude when near; while the probable error of a single measure in the “Harvard Photometry” was ±.17 of a magnitude, and in the “Uranometria Oxoniensis” about loof a magnitude. The large residuals in the “Harvard Photometry” appear to arise, according to Mr. Chandler, from the wrong identification of stars in many cases, one instance being cited where no bright star exists in or near the place given in the observing-list, on account of a misprint in the Durchmusterung, and yet some neighbouring star was observed on several nights for it. The author, in conclusion, pointed out that we must obtain better results from photometers if we ever expect to use their results for the detection or measurement of variable stars, since several variables have been detected, and their periods and light-curves well determined by eye-estimates, whose whole range of variation is no greater than the whole range of error in the photometric observations upon a single star with the meridian photometer.
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Our Astronomical Column . Nature 34, 531 (1886). https://doi.org/10.1038/034531a0
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DOI: https://doi.org/10.1038/034531a0