nti 
a 
85° 
~ Arr. XI; -ASTRONOMICAL AND NAUTICAL 
COLLECTIONS. 
No. XVII. 
i. Remarks on the Cavatocut of the Orbits of the Comets that have 
been hitherto computed. By Dr. Orzers. 
Tue Catalogue of the Orbits of Comets is founded on that which 
Delambre has given in the third volume of his Astronomy, p. 409. Many 
errors of the pen and of the press, in Delambre’s Catalogue, are corrected, 
and those orbits are added which were-unknown to Delambre, or over- 
looked by him, or which have been computed since the termination of -his 
catalogue in 1813. Where several persons have computed the orbits of the 
same comets, some of their results have been omitted, when they have been 
manifestly incorrect, or derived only from a construction, or given merely 
as examples of computation with inadequate observations, and by no means 
intended to represent the correct orbits. Perhaps, however, too many in- 
accurate computations have still been retained: but this has been done 
with the intention of affording a conjecture how far the orbit may be more 
or less remote from a parabola: and where the orbit has been found deci- 
dedly elliptical, it is interesting to compare the difference of the parabolic 
and the elliptic elements. And since so many orbits have now been com- 
puted as elliptic or hyperbolic, a separate column has been added for the 
eccentricities, Where this is left blank, the eccentricity is supposed to be 
= 1, or the orbit to be parabolic. The eccentricity shows whether the 
orbit is elliptic or hyperbolic, and thus renders the elements complete, 
since the greater axis is easily found from the eccentricity and the least 
distance. The logarithm of the mean motion is assigned in all cases, on 
account of its utility in computing the true anomaly, even in the cases of 
elliptic and hyperbolic orbits. For this logarithm of the mean motion we 
have retained, on account of uniformity, the constant logarithm 9.9601283, 
which has hitherto been commonly used, as the logarithm of the mean motion 
of a comet, of which the least distance is=1. This value supposes properly 
that the mass of the comet is equal to that of the earth: but if this mass, 
which is indeed unknown, but which is certainly always very inconsiderable 
became = 0, the logarithm should be 9.9601277:-so that if we required the 
ee possible accuracy, it would be necessary to diminish the tabular 
ogarithm of the mean motion by 6 in the 7th place of decimals. 
With respect to the following remarks on the table of comets, I must 
gratefully acknowledge the assistance that I have received from the excel- 
lent notes which the Baron von Zach and the Baron von Lindenau have 
respectively added to their tables. But for the sake of brevity, IT have 
omitted many references which may be found in Pingré, or in other works 
here quoted, and very extensively circulated. 
r No. Year. J 
1. 240. Chinese observations. A very uncertain orbit. Mon. Corr. X. 
. 167. 
2. 539. ae Chinese observations, without any latitudes. Mém. 
prés. 4 l'Inst. I. p. 290. Mon, Corr. II. p. 415. XVI. p. 498. 
_ 8. 565, Deduced from two Chinese observations only, upon the two 
suppositions, that the curtate distance of the comet, at the 
time of the first observation, was either = 1,2 or = 1.3, Al- 
