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muligens tilskrives l’jevnhed i Clironometrets Gang. men
saameget bliver tilbage som Fejl i Hojderne. at jeg anser
det rigtigst at antage, at mine Højder, med et rundt Tal.
kunne være beheftede med en sandsynlig constant Fejl for
hver Station af + 10".
Paa den Nøjagtighed, hvormed Observationsuhret
angiver Greenwich Middeltid. har jeg søgt at faa et Maal ved
følgende Overslag:
Observationsulirets Sammenligning med Hüveduhret.
Der toges flere Sammenligninger før og efter
Hojdeobser-vationerne. Af disse tinder jeg for 1877. mit Duplöxuhr,
en sandsynlig Fejl af den anvendte Uhrforskjel af + 0/15
(efter 4 Sammenligninger) og + 0/11 af 4
Sammenligninger før og 4 efter Observationerne. For 1878 finder jeg
for Sammenligningen mellem mit Lommechronometer og
Chronometer Reid saavel i Søen som i Havn. Middelfejlen
af en enkelt Sammenligning + 0/10. I Regelen gjordes
3 Sammenligninger, saaat Middelfejlen ved en
Sammenligning tør eller efter Højdeobservationerne kan sættes til
+ 0/06 og af Mediet af begge til + 0/04. Jeg kalder i
det følgende denne sandsynlige Fejl D{ og sætter med et
rundt Tal Dv = ± 0/1.
Naar Tidssignal skulde observeres, var Regelen den.
at Skibschefen. Capt. Wille, først sammenlignede
Observationsuhret. et Lommechronometer. der slog 0/4. med
Hoved-chronometret. derpaa gik i Land paa Telegrafkontoret og
efter Tilbagekomsten ombord atter tog en
Uhrsammenlig-ning. .leg antager, efter et Skjøn, denne Operations
Resultat at have en sandsynlig Fejl af + 0/1, som jeg kalder D2.
Paa Telegrafkontoret observerede Capt. Wille
Tids-signalerne efter Observationsuhret. Den sandsynlige Fejl
af Observationen af et enkelt ’Signal antager jeg at kunne
sætte til ^ 0/2. Da i Regelen neppe merç end 2 af de
3 Signaler kunne antages at blive godt observerede (ved de
2 sidste er man forberedt paa Secundet). sætter jeg den
sandsynlige Fejl af Resultatet af Observationen af
Tids-signalerne til + 0/15 (Di). Ved en Lejlighed, da vi begge
observerede Tidssignalerne. stemte vor Bestemmelse af
Ho-vedchrönometrets Stand paa 0/1.
Ved Signalets Afsendelse paa Observatoriet i
Christiania kan den sandsynlige Fejl, efter Vidnesbyrd fra
vedkommende Astronomer, sættes til 0/15 pr. Signal. + 0/10
pr. 2 Signaler (Di).
Ligeledes sættes den sandsynlige Fejl af
Normalpendelens beregnede Stand for Christiania Stjernetid.
corri-geret efter efterfølgende Tidsbestemmelse, til + 0/1 (D:,).
Den sandsynlige Fejl af den nedenfor antagne
Tids-forskjel mellem Christiania og Greenwich Observatoriers
Meridianer sættes til + 0/2 i D{J).
Ved Længdeberegningerne er forudsat en jevn Gang
hos Hovedchronometret mellem de Tidspunkter, da dets
• altitude amounting respectively to -|-8" and —’8". Some
part of this error may perhaps be ascribed to want of
uniformity in the rate of the chronometer: but even with this
deduction, the remainder is, I think, as an actual error in
the altitudes, sufficient to warrant assuming that my solar
altitudes may be affected by a -probable constant error at
each Station of + 10".
()f the precision with which the chronometer used
for noting the observations indicates Greenwich mean
time. I have sought to find a measure as follows: —
Comparison of the watch or chronometer selected for
the observation with the cWef time-keeper. Several •
comparisons were made before and after the observations of
altitude. Now. for 1877 (my duplex watch). I find a
probable error of the assumed difference of the. errors of the
time-pieces (4 comparisons) of + 0/15, and with 4
comparisons before ånd 4 after the observations, of + 0/11.
For 1878, I find the mean error of a single comparison
between my pocket-chronometer and the box-chronometer
by Reid. both at sea and in harbour, to have been + 0/10.
The number of comparisons having. as a rule been three,
the mean error of one comparison before or one after a
series of altitudes may be put ■at + 0/06, and the mean
error of two comparisons, one before and one after, at
+ 0/04. In the sequel I shall call this probable error
Z>i. and assume D{ — + 0/1.
The time-signals were generally observed as follows: —
Shortly before their arrival, the commander of the vessel.
Capt. Wille, compared a pocket-chronometer, beating 0/4.
with our chief time-keeper. He then went on shore to the
telegraph-office, observed the signals, and, on his return to
the ship, again compared the respective time-pieces. The
probable error of these comparisons on board may, I think,
be estimated at + 0/1, which I shall call D>.
At the telegraph-office Capt. Wille- observed the
time-signals with the pocket-chronometer mentioned above. The
probable error of the observation of one signal I have put
at + 0/2. Now, as only 2 of the 3 signals, on an average,
will be accurately observed (for the 2 last the observer is
prepared to the second). I shall estimate the probable error
of the result of our observations of the time-signals at + 0/15
(Di). On one occasion, when both of us (myself and Capt.
Wille) observed the time-signals, our determination of the
error of the chief chronometer agreed within 0/1.
According to the estimate of the astronomers of the
Christiania Observatory, the probable error of one signal
as given with the key at the Observatory may be put at
+ 0/15. of two signals + 0/10 (Di).
The probable error of the computed error of the
standard clock on Christiania sidereal time, corrected from
later transits of stars, is put at + 0/1 (/).,).
The probable error of the difference in time, as given
below.’ between the meridians of the Christiania and
Greenwich Observatories, is put at + 0/2 (A;).
For computations of longitude, the chief chronometer
is assumed to have had a uniform rate between the moments
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