of^ Douhk Stars. 4_^ 



^nly equal, but indeed fuperior, to having its right afcenfion 

 and declination given : for, fince it is to be viewed with very 

 high powers, not fnch as fixed inilruments are generally fur- 

 nifhed with, the given right afcenlion and declination would be 

 of no fervice. We might, indeed, find the iliar by a fixed or 

 equatorial inftrument ; and, taking notice of its (ituation with 

 regard to other neip;hbourinp fiars, find, and view it after- 



O O CD ' ' ^ 



Wards, by a more powerful telefcope ; but this will nearly 

 ftmount to the very fame way which here is purfued, with more 

 deliberate accuracy than we are apt to'ufe, while we are em- 

 ployed in feeking out an obje6l to look at. 

 ' It will be required, that the obferver fhould be furnidied 

 with Flamsteed's Atlas Cceleflis, which muft have the fliars 

 marked from the author's catalogue, by a number eafily added 

 to every flar with pen and ink, as 1 have done to mine. The 

 catalogue fhould alfo be numbered by an additional column, 

 after that which contains the magnitudes. I hope in fome 

 future editions of the Atlas to fee this method adopted in print, 

 as the advantage of it is wtty confiderable, both in referring to 

 the catalogue for the place of a ftar laid dow^n in the Atlas, and 

 in finding a ftar in the latter whofe place is given in the 

 former. 



I would recommend a precaution to thofe who wifh to exa- 

 mine the clofeft of my double ftars. It relates to the adjufl 

 ment of the focus. Suppofing the telefcope and the obferver 

 long enough out in the open air to have acquired a fettled tem- 

 perature, and the night fufficiently clear for thepurpofe; let 

 the focus of the Inftrument be re-adjufted with the utmofl 

 delicacy upon a ftar known to be fingle, of nearly the 

 fame altitude, magnitude, and colour, as the ftar which is to 

 be examined, or upon one ftar above and another - beloW the 



G 2 • fame. 



