H. Mobn. Astronomiske 



Observationer til Tids- og Steds- 



bestemmelse. 



De i denne Afhandling meddelte astronomiske Observa- 

 • tioner gjordes under Expeditionens Ophold i Havn 

 væsentlig- med det Maal tor Øjeat 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 geo- 

 grafisk Interesse, som paa Jan .Maven og Spidsbergen. Den 

 gunstige Lejlighed, som de gjemiem Telegrafen givne Tids- 

 signaler frembød til Yerirication af Længden af Punkter 

 paa Kysten af det nordlige Norge, ønskede jeg ogsaa at 

 benytte etter Lejligheden. 



Observationerne ere Solhøjder, maalte med Sextant. 

 Af Bestyreren for det astronomiske Observatorium i Chri- 

 stiania, Professor C Fearnley, lik jeg udlaant en < Observa- 

 toriet tilhørende Sextant af Troughton. med Kviksolvhori- 

 zuiit og Stativ, det samme Instrument, som Hansteen' be- 

 nyttede paa sin Rejse i Sibirien i Aarene 1828—1830, 

 I Brugen af Instrumentet niodtog jeg selv Prof. Hansteens 

 Vej ledning paa Observatoriet i 1861. Paa Sextanten af- 

 læses ved Nonien directe 10". Ved samtlige Observationer 

 benyttedes den lange Kikkert med ca. 10 Ganges Forstør- 

 ring. Olastaget over Kviksølvliorizonten provede jeg. paa 

 Røst, ved at stille det foran Kikkerten paa en Theodolitb, 

 der var indstillet paa en god Mire (et Kirkespir): Virk- 

 ningen af en prismatisk Form af Glassene var saagodtsom 

 umerkelig, og kan neppe udgjore et Par Sekunder. 



Saagodtsom alle de ber meddelte Observationer ere 

 gjorte med dette Instrument. Under Jan Mayen observe- 

 redes fra Skibsborde ogsaa med et Par andre Sextanter. 



Af Ubre bavdes i 187(3 ombord 3 Boxcbronometre. 

 af Kullberg, Frodsbam og Mewes samt et Lommechrono- 

 meter. formlen almindelige Lommeubre. hvoraf et mig til- 

 hørende Duplexubr. I 1877 og 1878 havde vi foruden de 

 nævnte Uhre et Boxcbronometer af Reid og i 1878 havde 



Den norske Nardhavsexpedition. H. Molm: Astronomiske Observationer, 



H. Molm. Astronomical Observations 



for determining Time, Latitude 



and Loiuritude. 



The astronomical observations set fortb in this Me- 

 moir were made during our stav in certain of the 

 harbours at which the Expedition toucbed, - - chiefly to 

 serve as a basis of the time and azimuth determinations 

 required for the magnetical observations. A secondary ob- 

 ject lav in performing. if possible. divers latitude and 

 longitude determinations that might prove of geograpbical 

 interest.. as. for instance. on the islands of Jan Mayen and 

 Spitzbergen. Moreover. ot the excellent opportunity aftbrded 

 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, Di- 

 rector of the Astronomical Observatory at Christiania, he 

 kindly lent mi' a. sextant belonging to that establishment. 

 one of Troughtohs. furnishéd with a mercury-horizon and 

 stand, - - the identical instrument used by Hansteen on his 

 travels in Siberia (1828—1830). In the use of the in- 

 strument Hansteen bad himself given me the necessary in- 

 structions. at the Observatory. in 1861. The vernier reads 

 10 seconds. For all the observations, the long telescope, 

 magnifying about 1U diameters, was exclusively used. Tlie 

 glass covering the mercury-horizon I tested at Pøst. 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 inappre- 

 ciable. 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 tåken on board 

 with other sextants. off the coast of .Jan Mayen. 



Of time-keepers. we bad on the first cruise, in 1876. 

 3 box-chronometers. made respectively by Kullberg, Frod- 

 sbam. 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 bad in addition a 



i 



