VOL. LXXV.] 



PHILOSOPHICAL TRANSACTIONS. 



649 



Sixth Class of Double Stars. 



VH. Observations of a New Variable Star. By Edward Pigott, Esq. p. 127. 

 For some years past I have been employed in verifying all the stars suspected 

 to be variable, that hereafter we may know with certainty what to depend on. 

 This undertaking, which is nearly completed, has already proved of use in de- 

 tecting many mistakes, and producing some discoveries ; among which, the fol- 

 lowing is one of the most important. Sept. 10, 1784, I first perceived a change 

 in the brightness of the star n Antinoi, and by a series of observations made ever 

 since, I find it subject to a variation very similar to that of Algol, though not 

 exactly the same in any one particular, -a Antinoi, when brightest, is of the 3d 

 or 4th magnitude, being between S and (3 Aquilae ; and at its least brightness of 

 the 4th or 5th magnitude, being then between that of i Antinoi and //. Aquilas; 

 therefore its greatest variation in brightness may be accounted about one magni- 

 tude ; and the changes it undergoes, though probably not nicely ascertained 



from so few observations, are nearly these an- 



,, , , . . , . . . At its greatest brightness 44 ± hours. 



nexed : all these changes, which hitherto seem In decreasing 62 ± . . . . 



to be regular and constant, are performed in 7 d At its least brightness . . 30 ± . . . . 



. . . T . „ ... .. • , n increasing 36 ± . . . . 



4 h 38 m ; and this I shall stile its period. 



VOL. XV. 



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