Maximilianus Hell (1720-1792) - Munin

Incidentally, Hell’s final conclusion concerning the latitude of his observatory – 70º 22′ 36″ –
is today found to be somewhat more inaccurate than his determination of the longitude.
According to Bjørn Geirr Harsson at Statens Kartverk (‘Norwegian Mapping and Cadastre
Authority’), the astronomical latitude should be 70º 22′ 15.5″ N, that is, 20.5 seconds, or 632
meters further south than Hell’s figure. It is important to note, however, that this modern
value depends on a more accurate knowledge of the curvature of the Earth’s surface than that
which existed in the eighteenth century. 66 An overall examination of Hell’s activities as a
surveyor during his expedition, with assessments of his results in the light of the history of
Nordic geodesy, is a desideratum. 67
In any case, Maximilianus Hell felt that he had safely determined the latitude of his
observatory, when the third day of June 1769 approached. The running of the clocks had
already been tested for weeks, and the frequency of these tests was intensified in the last days
before the transit. Ideally, such tests involved observations of the Sun as it passed the
meridian in the South at noon and the meridian in the North at midnight. The transit was
going to take place when the Sun was in the North, meaning that the northern room of his
observatory (the observatoriolum septentrionale) would be used for this crucial observation.
Having checked the time keeping at twelve o’clock in the day, Hell had to move his
instruments over to the northern chamber in the afternoon of 3 June in order to be prepared for
the transit of Venus. By the next morning – 4 June – at least two of his telescopes must have
been moved back again, as these were used to observe the eclipse of the Sun, which took
place between 9:22 and 11:22 am, and would only be visible from the observatoriolum
australe. 68
66 Bjørn Geirr Harsson (pers.comm.). The astronomical latitude, observed by Hell, is related to the plumb line at
the station, whereas the latitude obtained from a GPS receiver is related to the normal at the ellipsoid. “The angle
between the plumb line and the vertical of the ellipsoid is called the deflection of the vertical,” Harsson explains.
“In Vardø the geoid is tilting to eastnortheast, which means that the deflection of the vertical has a component in
direction north, even if the main component is in direction east. The north component of the deflection of the
vertical is computed to be 2.5 second of an arc at today’s post office in Vardø. So if 2.5″ is added to the GPSlatitude,
the two latitudes can be compared. Hell’s latitude was 70º 22′ 36″ and the GPS-latitude is 70º 22′ 13″. If
we add the 2.5″ to the GPS-latitude we get 70º 22′ 15.5″. The difference of 20.5 seconds corresponds to a
latitude for Hell to be 632 meters north of today’s GPS position of the same place” (pers.comm.).
67 An investigation of the latitude for a single location (in Christiania, now Oslo) by Harsson in 2003 gave a
discrepancy of only nine arc seconds, or 270 meters between Hell’s determination and the modern value (Aspaas
and Voje Johansen 2004a, pp. 5-6). It would be futile, however, to conclude much from the examples of Oslo
and Vardø alone.
68 Cf. Hell 1770a1, p. 81.
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