of Double Stars. 44 
Duly equal, but indeed fuperior, to having its right afcenfion 
■and declination given : for, fince it is to be viewed with very 
high powers, not fuch as fixed inflruments are generally fur- 
iiifhed with, the given right afcenfion and declination would be 
of 110 fervice. We might, indeed, find the fiat by a fixed or 
equatorial inflrumenf ; and, taking notice of its fituation with 
regard to other neighbouring flars, find, and view it after- 
wards, by a more powerful telefcope ; but this will nearly 
amount 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 objedt to look at. 
It will be required, that the obferver fbould be furnifhed 
with Flamsteed’s Atlas Cceleflis, which muff have the flats 
marked from the author’s catalogue, by a number eafily added 
to every flat with pen and ink, as 1 have done to mine. The 
catalogue fbould 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 very confiderable, both in referring to 
the catalogue for the place of a flar laid down in the Atlas, and 
in finding a flar in the latter whofe place is given in the 
former. 
I would recommend a precaution to thofe who wifh to exa- 
mine the clofefl of my double flats. It. relates to the adjufi 
ment of the focus. Suppofmg 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 the purpofe ; let 
the focus of the inflrument be re-adjufled with the utmo.fl 
delicacy upon a flar known to be fingle, of nearly the 
fame altitude, magnitude, and colour, as the flar which is to 
be examined, or upon one flar above and another below’ the 
G 2 
fame. 
