234 



KNOWLEDGE 



[October 2, 1899. 



T Corons. — A small star following this binary (51", 1802) 

 was rated only 15 or 20 magnitude by South in 1825, but 

 " more like 10 magnitude " by Franks in 1876. I have 

 seen this small star well with a 3 -inch refractor in the 

 Punjab sky. 



In 1862, Tebbutt, while observing Comet III. of that 

 year, noticed a star of 5th magnitude about " a degree 

 north-east " of o- Arae. Both stars were visible to the 

 naked eye, the supposed variable being the brighter of the 

 two. On examining the place of the star with a 4i-inch 

 reflector on November 18th, 1877, Tebbutt only found 

 stars of the 10th and 11th magnitudes near the spot. One 

 faint star particularly attracted his attention, and its 

 position agreed fairly well with that of the 5th magnitude 

 star observed in 1802. There are some other faint stars 

 near the place. As Tebbutt's 5th magnitude star lay in 

 the Milky Way, it was probably a Nova, or " temporary 

 star." 



A star close to the Durchnmsterumj star, 17^', 3997, was 

 rated 6, 6, and 6-5 magnitude by d'Agelet on July 26th, 

 27th, and 29th, 1783, but is not given by Lalande or 

 Harding. In 1882 and 1883, Dr. Chandler failed to see 

 any trace of a star in d'Agelet's position with a 6^-inch 

 reflector, and found it invisible with 15-inch refractor, 

 November 14th, 1883. On September 18th, 1884, the 

 present writer could see no trace of the star with a 

 binocular in a clear sky. Have we here another Novo ' 



About 2|- south pircedi 11(1 cr Capricorni, 8ir John Herschel 

 observed a red star, which he rated 6| magnitude, and 

 says, " A fine ruby star. This is perhaps the finest of my 

 ruby stars." I failed to see this star with an opera glass 

 in July, 1875, and with 3-inch refractor found it only 8| 

 or 9 magnitude, and fiery red. In November, 1876, and 

 August, 1879, I found it about the same magnitude. If 

 Herschel's estimate of 6i magnitude was at all correct, 

 the star must certainly be variable. Closely following, a 

 little north, is a fainter star about 10 or 10^ magnitude. 

 Variation was also suspected by Secchi, and he estimated 

 the star 7-5 magnitude on July 15th, 1868, and deep red ; 

 7 magnitude, September, 1869. It was rated magnitude 

 by Webb on September 8rd, 1873, and 7-5 magnitude by 

 Birmingham. Espin found it 7'3 magnitude on September 

 4th, 1882 ; 7-0 August 29th, 1883, and 7-1 on September 

 21st, 1883, and thinks it is " probably a variable of the 

 19 Piscium type." 



7 Aquarii. — This star may possibly be variable. It 

 was rated of the 8rd magnitude (!) by Ptolemy, 6 mag. by 

 Al-Sufi (10th century), 5 by Argelander, and 6-5 by Heis. 

 In Schjellerup's translation of Al-Sufi's Persian manu- 

 script, its position is thus described : — " La 0" (7 Aquarii) 

 est la suivante des trois I'toiles situees danslamain gauche, et 

 precede la 4^ (/? Aquarii) qui se trouve sur I'epaule gauche ; 

 elle est de la sixieme grandeur, tandis que Ptolemee la dit 

 de troisieme, mais en verite, elle est tres obscure. La 

 7' (/A Aquarii) se trouve au milieu de ces trois etoiles et 

 precede la G', s'iuclinant vers le nord ; elle est de petites 

 de la cinquieme grandeur ; Ptolemee la dit de quatrieme. 

 Entre elle et la 6' il y a environ un empan. La 8- (e Aquarii) 

 est la precedente des trois et des grandes de la quatrieme 

 grandeur; Ptolenu'e la dit de troisieme." A glance at a 

 star map will show that Al-Sufis description is accurate, 

 and proves that the star numbered 6 by Al-Sufi is identical 

 with that numbered 7 by Flamsteed. Sir William Herschel 

 found it less than /x but considerably brighter than 8 (Fl.) 

 (Aquarii). It was rated 5-9 mag. by Gould, who suspects 

 variation. It was measured 5'09 with the photometer at 

 Harvard. 



Sir William Herschel published in the Philosophical 

 Transactions of the Koyal Society for the years 1796, 1797, 



and 1799 a series of observations of the relative " lustre" 

 of the stars in Flamsteed's Catalogue. In recently going 

 through these interesting and valuable records of the 

 comparative brightness of the stars at the close of the 

 eighteenth century, and comparing Herschel's sequences 

 with modern estimates and photometric measures, I have 

 noticed a considerable number of suspicious cases. The 

 following are perhaps the most remarkable and interesting;. 



With reference to the stars 30, 33, and 35 Arietis, 

 Herschel gives the sequence 85, 30-83, which denotes that 

 35 was just perceptibly brighter than 30. and 30 a little 

 brighter than 33. Herschel also gives 39, 35, 33. Now, 

 according to the photometric measures made at Harvard, 

 Oxford, and Potsdam, 83 is fainter than 35 but decidedly 

 brighter than 30 . 30 may therefore be variable. It is a 

 double star — Struve I. 5 — and the magnitudes of the com- 

 ponents (which are 38'6" apart) have been variously esti- 

 mated by difierent observers. Struve gives them 61 and 

 7-1, or one magnitude difference, the fainter star preceding 

 the other. Main found them equal in brightness in 1863 ; 

 Dembowski rated them 5-4 and GO. Sadler thought there 

 was not one magnitude difference in 1874, and Franks 

 not more than half a magnitude in 1870. The photo- 

 metric measures of the pair made at Oxford and Potsdam 

 are discordant ; those made at Oxford giving 6-33 and 

 G'78, or the preceding star the brighter, while the Potsdam 

 measures gives 7-24 and 6-82, or the -preceding star the 

 fainter. This seems to show distinct variation, and the 

 object should be further observed. 



With reference to the stars in the Lynx, Herschel gives 

 the sequence 22 — 21 - - 20, denoting that 22 Lyncis 

 was a little brighter than 21, and 21 considerably brighter 

 than 20. Now the photometric magnitudes of these stars 

 measured at Harvard are 22 == 5'37 magnitude, 21 = 4-57, 

 and 20 = 0-57, or 22 considerably ,/af»te*- than 21. 21 was 

 estimated 5th magnitude by Argelander and Heis, and 22, 

 6th magnitude. The Durchm listening also makes 21 

 brighter than 22 — by H magnitudes. Hence it appears 

 that, if Herschel's sequence was correct (and most of his 

 comparisons of relative brightness compare very favourably 

 with modern measures), either 22 or 21 Lyncis is variable 

 in light. These stars should be watched by variable star 

 observers. 



Atieminorum. — In the notes to his catalogues Herschel 

 says this star "seems to be increasing. There is an 

 interval of nine months between the two observations of 

 my catalogue. Mr. Bode supposes the star to be change- 

 able." The Harvard measures make it very slightly 

 brighter than 8 Geminorum, while the Oxford and Potsdam 

 measures make it slightly less. Both Argelander and 

 Heis make A perceptibly fainter than 8, and so does the 

 Durrhmusterung. The Potsdam measures vary between 

 3-5 and 41, and the star may possibly be variable to 

 a small extent. 



Herschel found t- (81) Geminorum only slightly brighter 

 than gi (30), while Argelander, Heis. and the Harvard and 

 Oxford measures agree in making t- about ly magnitude 

 brighter than £'. 



/3 and i; Herculis. — Sir W. Herschel suspected both 

 these stars to be variable. His observations make /3 

 sometimes distinctly brighter than ?, and sometimes 

 distinctly fainter. With reference to p he says, " By my 

 observations the light of this star seems to be subject to 

 change. Flamsteed's observations give it twice 3 m., and 

 once 2 m." And with reference to ?, he says, " From the 

 expressions I have given of the brightness of this star, we 

 have great reason to suppose it to be changeable." The 

 Harvard and Potsdam measures make p slightly the 

 brighter of the two, and so do Argelander and Heis. 



