DECLINATION, 
"The ecorre&tions to be applied to die obfervation of the 
meridian altitude of a fixed flar to find its mean — tion 
at the beginning of the year, are thofe depending on refrac- 
ron a aberration, nutation, and f{emi. ane folar 
When it is intended to bree the fame ftars ig baa 
3t will be found very convenient to make a table of their 
mean refraétions, with the change for each degree of the ther- 
mometer, and for each tenth of an inch of the ba arometer, ag 
given in Mr. Wollatton’s tables, which are here {ubjoined 
af. 
Example. ¥ Pega 
: Oblervation 
Cor. for Refra&. Barom.} Ther.| Refrac. 
| 218co. | nche ; 
‘Nov. 3. }142° go! 27.5 | 29.2 | 51° | 42’.48 
7: 37 9 27 Re 29.2 5A 42 Br 
OR tL 37 9 26 Q 29.6 48 43 37 
Mean refraction ——- As" ae 
Barometer - nah 
Thermometer "e WI 
Nov 3. : 142° se | 
Nov. 7 and 11, or Nov. 9. 
Sum - E 
a7 27-4 
aA 9 5 9 
: 5 —_ 
Error of ha . - 2655 
rae ae = 37 9 29.95 
aia a €c. ; ; +25: a) +23. 7 
37 3s 
Co. lat. . - _ 38 Pr e : 
Polar diflance, Jan. 1800 4 e ee 365 i 
a Lyre. 
| Obiervation. | Bar. | Pher. | Ret. 
| 
2" 
12.6 
122 37'42".6 
167 22 9.6 
29".9 So 
29-2 5 { 
Mean oe ro" .7 5 
Barom - ot 
Ginoaces : - 03 
12° 34! 42".6 
167 22 
372 $9 $22 
180 
78 
Error of coll. » - 3.9 
12 37 46.5 
Ab. and Pree. - - + 15.3 
Nut. - = * 8.3 } + 7 
~ Carried over 12 37 53-5 
Brought over 12 gy? 53" 5 
45 43 
Polar dift. Jan. t8cO = =r 23 36.8 
ken the patie altitude or zen. difkance of a planct is 
me ved: the calcu pe n for finding its declination differs 
ut little eon ao a fix ed ftar r except that the correction 
for parallax and a _ ration muft b e taken from the tables 
of the planet. If one of the principal fixed ftars pafles 
nearly at the fame time, differing but little in. cae the 
declination of the planet = better be calculated by com- 
paring it with the coe 
Obfervations made oe mine the declination of the 
moou require fome correétions that fhould ie particularly ex- 
plained. It is ufual to obferve either the upper or lower 
imb. If we with to know what would been the ob- 
Jerved altitude of the centre, we mut employ 
ter augmented according to its altitude, oe “diminifhed by 
ed oS a piace correfponding to the limb and the 
3 OF, W y proceed to calculate the declination of 
she hier limb, This latter method we think preferable 
to the 
The soneeiah for parallax varies according to the altitude. 
on, aud is fubje& toa {mall equation depending. 
of the mo 
on the latitude of the eect as wil be more fully explained 
da 
ugh for the pape purpofe will be. 
underftood by rete to Plate V. fig. 4 
O reprefents the eee of the cbferen on the elliptic 
meridian, e normal o ontinuation of 
; the saa the angle 
com no O The declination of the aa limb re- 
quired is the an ale M CE. he moon were in the lin 
Z O, it would have no parallax, and its zenith dillance would 
equal the a which the vertical, O m, makes with the ra- 
us. moon bla in oe zenith Z, it would never- 
thelefs ce a {mall para 
The equatorial sails a be diminifhed in the propor- 
tionof EC to OC, 
Example, taken from the Greenwich Obfervations. 
Sept. 1. 1806. The zenith diftance of the moon’s upper 
limb was obferved 38° 48! 32 The error of collimation 
was 2.9, and the error of the arc, Sasa note . obfervas 
tions) was 1” additive. The refraction w . 
Thefe corre€tions make the zenith haces ta 49' 21/3. 
The equatorial parallax by the tables was at that time’ 
’ 30"; this dimmithed i in the proportion of EC toOC 
{ y Table XX.)is 55’ 24”, which is the horizontal cei 
lax at Greenwich : : this pecan ~ the fine of the zenith 
the radius rage with the 
angle XX.) gives 
r the parallax in alt. en is to be fub- 
tracted from the zenith diftance, and leaves 38° 14’ 45".1. 
The fame tables which give the equatorial parallax 
55’ 30”, give the femidiameter 15! 8”.8, which added to the 
lea 
rab 124 st 
8 . 1806. 
