C 457 3 
XXVII. Catalogue of One Tboufand new Nebula and Clujlen of: 
Stars, By William Herfchel, LL.D, F. R. S* 
Read April 27, 1786* 
T HE following Catalogue, which contains one thoufand 
new Nebulae and Gutters of ftars, is extracted from a 
feries of obfervations (or Sweeps of the heavens), which was 
begun in the year 1783, and which I am ftill continuing till 
the whole be completed. As I may, perhaps, find an oppor- 
tunity hereafter to publifh thefe obfervations at full length, I 
fliall now only mention fuch circumftances, relating to the 
inftrument and apparatus with which they were made, as will 
be neceffary to fhew what degree of accuracy may be expe&ed 
in the determination of the places of thefe Nebulae and Clutters 
of ftars; and alfo to ferve any aftronomer, who wifhes to 
review them, to form a judgment what inftrument will fuffice 
for this purpofe. 
The telefcope I have ufed, as has been obferved on a former 
©ccafion^, is a Newtonian reflector of 20-feet focal length, 
and 18-/-^ inches aperture. The fweeping power has been 157, 
except where another is exprefsly mentioned. The field of 
view 15' 4". 
My eye-glafs is mounted on that fide of an octagon tube, , 
which, in the horizontal pofition of the inftrument, makes an 
angle of 45 0 with the vertical ; having found, by experience, 
that this pofition, refembling the fituation of a reading defk, is * 
* Philofophical Tranfa&ions, vol. LXXIV. p. 437. 
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