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H. Molin. Astronomiske
Observationer til Tids- og
Stedsbestemmelse.
De i denne Afhandling meddelte astronomiske
Observa-• tioner gjordes under Expeditionens Ophold i Havn
væsentlig med det Maal for Øje’ at tjene til Grundlag for
de Tids- og Azimuthbestemmelser. der udfordredes til de
magnetiske Iagttagelser. Ved Siden deraf tilsigtedes ogsaa
Bredde- og Længdebestemmelser, der kunde være af
geografisk Interesse, som paa .Tan Maven og Spidsbergen. Den
gunstige Lejlighed, soin de gjennem Telegrafen givne
Tidssignaler frembød til Verification af Længden af Punkter
paa Kysten af det nordlige Norge, ønskede jeg ogsaa at
benytte efter Lejligheden.
Observationerne ere Solhøjder, maalte med Sextant.
Af Bestyreren for det astronomiske Observatorium i
Christiania, Professor C. Fearnley, fik jeg udlaant en
Observatoriet tilhørende Sextant at’ Troughton. med
Kviksølvhori-zont og Stativ, det samme Instrument, som Hansteen
benyttede paa sin Rejse i Sibirien i Aarene 1828—1830.
I Brugen af Instrumentet modtog jeg selv Prof. Hansteens
Vejledning paa Observatoriet i 1861. Paa Sextanten
aflæses ved Nonien directe 10". Vecl samtlige Observationer
benyttedes den lange Kikkert med ca. 10 Ganges
Forstørring. Glastaget over Kviksølvhorizonten prøvede jeg, paa
Røst. ved at stille det foran Kikkerten paa en Theodolith,
der var indstillet paa en god Mire (et Kirkespir);
Virkningen af en prismatisk Form af Glassene var saagodtsom
umerkelig, og kan neppe udgjøre et Par Sekunder.
Saagodtsom alle de her meddelte Observationer ere
gjorte med dette Instrument. Under Jan Mayen
observeredes fra Skibsborde ogsaa med et Par andre Sextanter.
Af Uhre havdes i 1876 ombord 3 Boxchronometre,
af Kuliberg, Frodsham og Mewes samt et
Lommechrono-meter, foruden almindelige Lommeuhre. hvoraf et mig
tilhørende Duplexuhr. I 1877 og 1878 havde vi foruden de
nævnte Uhre et Boxchronometer af Reid og i 1878 havde
Den norske Nordliavsexpedition. H. Moliu: Astronomiske Observatic
H. Mohn. Astronomicai Observations
for determining Time, Latitude
and Longitude.
The astronomical observations set forth in this
Memoir were made during our stay in certain of the
harbours at which the Expedition touched, — chiefly to
serve as a basis of the time and azimuth determinations
required for the magnetical observations. A secondary
object lay in performing, if possible, divers latitude and
longitude determinations that might prove of geographical
interest,, as, for instance, on the islands of Jan Mayen and
Spitzbergen. Moreover, ol the excellent opportunity afforded
by the telegraph time-signals to verify the longitude of points
on the northern line of the Norway coast, I was specially
desirous of taking advantage.
The observations are solar altitudes, measured with
the sextant. On application to Professor C. Fearnley,
Director of the Astronomical Observatory at Christiania, lie
kindly lent me a sextant belonging to that establishment,
one of Troughton’s, furnished with a mercury-horizon and
stand, — the identical instrument used by Hansteen on his
travels in Siberia (1828—1830). In the use of the
instrument Hansteen had himself given me the necessary
instructions. at the Observatory, in 1861. The vernier reads
10 seconds. For all the observations, the long telescope,
magnifying about 10 diameters, was exclusively used. The
glass covering the mercury-horizon I tested at Røst. by
placing it in front of the telescope of a theodolite directed
to a good mark (a church steeple). The effect resulting from a
slightly prismatic form in the glasses was well-nigh
inappreciable, amounting as it did to hardly a couple of seconds.
Almost all of the observations were made with this
instrument, å very few only having been taken on board
with other sextants, off the coast of Jan Mayen.
Of time-keepers, we had on the first cruise, in 1876.
3 box-chronometers, made respectively by Kullberg,
Frodsham. and Mewes. and a pocket-chronometer, exclusive of
watches, one of which — that belonging to myself — was
a duplex lever. In 1877 and 1878. we had in addition a
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