ASTRONOMY. 
ethers. From thence he computed the latitudes and lon¬ 
gitudes. Tycho compared Venus with the Sun, and then 
the other ftars with Venus, allowing for its parallax and 
refrattion ; and, having thus afcertained the places of a 
few (tars, he fettled the reft from them; and although his 
inftrument was very large, and conftruCted with great ac¬ 
curacy, yet, not having pendulum-clocks to meafure his 
time, his obfervations cannot be very accurate. The next 
catalogue was that of R. P. Riccioius, which was taken 
from Tycho’s, except ioi ftars which he himfelf had ob- 
ferved. Hevelius, in 1690, publilhed a catalogue of 1930 
ftars, of which 950 were known to the ancients; 603 he 
calls his own, becaufe they had not been accurately obfer- 
ved by any one before himfelf; and 377 of Dr. Halley 
which were invilible to his hemifphere. Their places 
were fixed for the year 1660. The Britifh Catalogue, 
which was publiftied by Mr. Flamftead, contains 3000 
ftars, redified for the year 1689. They are diftinguiftied 
into feven degrees of magnitude (of which the feventh de¬ 
gree are tele(copic) in their proper conftellations. This 
catalogue is more correCt than any of the others, the ob¬ 
fervations having been made with better inftruments. He 
alfo publiftied an Atlas Ccclejlis, or Maps of the Stars, in 
which each ftar is laid down in its true place, and delinea¬ 
ted of its own magnitude. Each ftar is marked with a 
letter, beginning with the firft letter of the Greek alpha¬ 
bet for the largeft ftar of each conftellation, and fo on ac¬ 
cording to their magnitudes, following, in this refpeft, the 
charts of the fame kind that were publiftied by J. Bayer 
in 1603. In the year 1757, M. de la Caille publiftied his 
Fundamenta Aftrononiide, in which there is a catalogue of 
397 ftars; and, in 1763, he publiftied a catalogue of 1942 
iouthern ftars, from the tropic of Capricorn to the fouth 
pole, with their right afeenfions and declinations for 1750. 
He alfo publiftied a catalogue of the zodiacal ftars in the 
Ephemerides, from 1765 to 1774. Mr. Mayer alfo pub¬ 
liftied a catalogue of 600 zodiacal ftars. In the Nautical 
Almanac, for 1773, there is publiftied a catalogue of 380 
ftars, obferved by Dr. Bradley, with their longitudes and 
latitudes. In the year 1782, J. E. Bode, aftronomer at 
Berlin, publiftied a fet of Celeftial Charts, containing a 
greater number of ftars than in thofe of Mr. Flamftead, 
with many of the double ftars and nebulas. He alfo pub¬ 
liftied, in the fame work, a catalogue of ftars, that of Flam¬ 
ftead being the foundation, omitting fome ftars whole po- 
fitions were left incomplete, and altering the numbers of 
others ; to which he has added ftars from Hevelius, M. 
de la Caille, Mayer, and others. In the year 1776, there 
was publiftied at Berlin, a work entitled, Recueil de Ta¬ 
bles Aftronomiques, in which is contained a very large ea- 
talogueof ftars from Hevelius, Flamftead, M. de la Caille, 
and Dr. Bradley, with their latitudes and longitudes for 
the beginning of the year 1800 ; with a catalogue of the 
iouthern ftars of M. de la Caille; of double ftars; of 
changeable ftars ; and of nebulous ftars. This is a very 
ufeful work for the practical aftronomer. But the moll 
complete catalogue is that publiftied by the Rev. Mr. Wol- 
lafton, F.R.S. in 1789, entitled, “ A Specimen of a Gene¬ 
ral Aftronomical Catalogue, arranged in Zones of North 
Polar Diftance, and adapted to January 1, 1790 ; contain¬ 
ing a Comparative View of the Mean Pofitions of Stars, 
Nebulae, and Cinders of Stars, as they come out upon 
Calculation from the Tables of feveral principal Obfer- 
vers.” By arranging the ftars into zones parallel to the 
equator, an obferver, with his telefcope on an equatorial 
ftand, will have the ftars pafs through in the order in which 
he finds them in the catalogue, by which he will more 
readily find out what he wants, being prepared for its ap¬ 
pearance. The firft table contains a catalogue of the mean 
right afeenfions of thirty-fix principal ftars for January 1, 
1790, as fettled by Dr. Mafkelyne, with their annual pre- 
ceftions, and proper motions. The fecond table contains 
the general catalogue of ail the ftars whofe places have 
been well afcertained, together with thofe nebulae and 
clutters of ftars which can «afily be feen by a good coin- 
4 Z 7 
mon telefcope, with their right afeenfions and north polar 
diftances, and their annual preceffions; alfo their magni¬ 
tudes, and the number, name, or character, of the objeCt, 
and by whom it was obferved. T he third table contains 
an index to the ftars in the Britifti Catalogue ; referring to 
the zone of north polar diftance in which each is to be 
found. The fourth table contains an index of thofe ftara 
in M. de la Caille’s fundamental catalogue which are not 
in Flamftead’s. The fifth table contains Flamftead’s Bri- 
ti(h Catalogue, and M. de la Cailie’s fouthern catalogue, 
with about eighty circumpolar ftars from Hevelius which 
had been omitted by Flamftead, arranged in their order of 
right afeenfions in time for January 1, 1790. The fixth ta¬ 
ble contains a catalogue of the zodiacal ftars for nine de¬ 
grees of latitude, arranged in their order of longitude for 
January 1, 1790. The whole concludes with a plan for 
examining the heavens, propofing that different perfons 
ftiould undertake different zones and examine them very 
minutely ; recommending a fyftern of wires in a telefcope 
which he has found very convenient for that purpofe. The 
practical aftronomer is under very great obligations to Mr. 
Wollafton for fo ufeful and complete a work. 
In all the preceding catalogues, aftronomers have been 
led to arrange the ftars in clashes of different magnitudes 
by their various degrees of brilliancy, or luftre. Briglit- 
nefs and iize have hitherto been confidered as fynonymous 
terms ; fo that the brighteft ftars have been referred to the 
clafs comprehending thofe of the firft magnitude ; and, as 
the fubfequent orders of ftars have been fuppofed to de- 
creafe in luftre, their magnitude has been determined in 
the fame decreafing progrelfion : but (till, Dr. Herfchel 
obferves, the want of fome fixed and fatisfaCtory ftandard 
of luftre has been the fource of confiderable confution and 
uncertainty, in fettling their relative magnitudes. A ftar, 
marked 1. 2m. is fuppofed to be between the firft and“fe- 
cond magnitude ; but 2. im. intimates that the ftar is near¬ 
ly of the fecond magnitude, and that it partakes fomewhat 
of the luftre of a ftar of the firft order. Such fubdivifions 
may be of life in afcertai.ning ftars of the firft, fecond, and 
third, clafles: but the expreUions 5m. 5. 6111. 6. 5111. 6m. 
are often very vague and indefinite. Dr. Herfchel ob¬ 
ferves, that he has found them fo in faCt; and he there¬ 
fore confiders this method of pointing out the different 
lujlre of ftars as a reference to an imaginary ftandard. If 
any dependence could be placed on this method of mag¬ 
nitudes, “ it would follow (fays he), that no lefs than ele¬ 
ven ftars in the conftellation of the Lion, viz. /?, cr, •n, 
A, b, c, d, 54, 48, 72, had all undergone a change in their 
luftre fince Flamftead’s time. For, if the idea of magni¬ 
tudes had been a clear one, our author, who marked /3 r. 
2nt. and 7 2m. ought to be underftood to mean /3is larger 
than 7; but we now find that actually 7 is larger than 
Every one of the eleven ftars I have pointed out may be 
reduced to the fame contradiction.” 
Dr. Herfchel points out feveral inftances of the infuffi- 
ciency of this method, and of the uncertain conclufions 
that are deduced from it, in determining the comparative 
brightnefs of ftars found not only in Mr. Flamftead’s ca¬ 
talogue, but alfo in the catalogues of other aftronomers j 
he therefore propofes a different mode, that is.more pre- 
cife and fatisfaCtory. “ I place each ftar, (he fays,) in- 
ftead of giving its magnitude, into a (Fort feries, conftruct- 
ed upon the order of brightnefs of the neareft proper ftars. 
For inftance ; to exprefs the luftre of D, I fay C D E. 
By this ihort notation, inftead of referring the ftar D to an 
imaginary uncertain ftandard, I refer it to a precife and 
determined exifting one. C is a ftar that has a greater 
luftre than D, and E is another of lefs brightnefs than D. 
Both C and E are neighbouring ftars, chofen in ftich a 
manner that I may fee them at the fame time with D, and 
therefore may be able to compare them properly. The 
luftre of C is in the fame manner afcertained by B C D; 
that of B by ABC; and alfo the brightnefs of E by 
DEF; and that of F by E F G. 
“ That this is the moft natural, as well as the mod ef¬ 
fectual, 
