of Douhle Stars. ^c 



Ali the obfervations in the following catalogue on the rela- 

 tive magnitude, colour, and potition of the (tars, are to be 

 underflood as having been made with a power of 460, unlels 

 they are marked otherwife. This will account- for the dif- 

 ference wliich obfervers may find in the relative magnitude ; for 

 fhould they ufe only a power of about 200, many of the 

 fmall ftars that are faid to be very unequal and extremely une- 

 qual, mull: appear to them perhaps a degree lower in the fcale, 

 and become extremely and exceffively unequal : and this will 

 happen, though the quantity of light fhould be the very fame 

 which the reflector has that ferved me to fettle thefe particulars. 

 I need not fay, that on other accounts, fuch as a real difference 

 in the light of the telefcope, the prefence of the moon, twi- 

 lights, auroras boreales, or other caufes,, many of the fmall 

 flars may be found to be of a different comparative luflre from 

 what is alligned to them in the catalogue. The fmall ftar near 

 Rigel, for inflance, appears of a beautiful pale red colour, full, 

 round, and well defined, with my 20-feet reflector; the lo-feet 

 inftrument fhews it alfo very well in fine evenings ;. the ^-feet 

 requires more attention, nor is the fmall flar defined, but of a 

 dulky pale red colour. A good 3I feet achromatic, of a large 

 aperture, when Rigel is on the meridian^ tT^^Y? perhaps, alfo 

 ihew the fmall flar, although I have not been able to fee it 

 with a very good initrument of that fort, which fhew^s the 

 fmall ftar that accompanies the pole-flar ;, but the evening was. 

 not very favourable. 



The meafures of the diftances were all taken with a parallel 

 filk-worm'^s- thread micrometer, and a power of 227 only.. 

 They are not, as in the former catalogue, with the diameters 

 included, but from the center of one flar to the center of the 



othcr^ 



