DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20131#0134
114
ASTRONOMICAL DETERMINATIONS OF LATITUDES AND LONGITUDES.
The latitude and longitude of Pashmin is deduced approxiinatively from our
itineraries; but this eclipse could be referred by chron. 3 directly to Srinagger, the
rate of the chronometer being very well known, and the time being determined soon
after our arrival in Kashmir, October 24 and 25.
Though from eclipses of the moon longitudes cannot be deduced with the greatest
precision, on account of the phenomena to be observed not being sufficiently well
defined, these observations were nevertheless of particular interest from the nature of
the physical phenomena attending this present eclipse.
In eclipses, the atmosphere produces, besides the shadow of the earth itself, an-
other secondary shadow, which veils, as it were, the shadow proper of the earth in
forms often indistinct and diffused, and modified by atmospherical phenomena, such
as clouds, haze, &c.
According to circumstances, the forms of this atmospheric shadow are variable in
each eclipse, being sometimes spherical, and at other times of very irregular curvatures.
The magnitude also of this shadow is extremely variable, on some observed occasions
extending over a space of three minutes of arc, as in the year 1772, on others of one
minute, as in 1773, and sometimes even less. The magnitude of the penumbra itself
is also subject to similar variations. It was observed to precede the nucleus of the
shadow from 2 to 10 minutes of time; in April, 1818, it even preceded the nucleus
by 15 minutes.
For 1856, when I (Hermann) had occasion to observe the moon's eclipse, no such
observations by others of the magnitude of the penumbra are known to me.
I found the magnitude of the penumbra equal to the semi-minor axis of the Mare
crisium. According to various observations, the shadow of the earth itself required
the following times for passing through the whole breadth of Mare crisium:
Observer. Time.
m s
Neumayr..................... 622
Niebour...................... 7 0
Riimker...................... 541
Schmidt...................... 7 10
Mean .... ." 6 34
Half the value of this time is 3m 17s, and this value of the magnitude of the
penumbra I adopted for the calculation of longitude from occupations of Tycho and
Mare crisium.
ASTRONOMICAL DETERMINATIONS OF LATITUDES AND LONGITUDES.
The latitude and longitude of Pashmin is deduced approxiinatively from our
itineraries; but this eclipse could be referred by chron. 3 directly to Srinagger, the
rate of the chronometer being very well known, and the time being determined soon
after our arrival in Kashmir, October 24 and 25.
Though from eclipses of the moon longitudes cannot be deduced with the greatest
precision, on account of the phenomena to be observed not being sufficiently well
defined, these observations were nevertheless of particular interest from the nature of
the physical phenomena attending this present eclipse.
In eclipses, the atmosphere produces, besides the shadow of the earth itself, an-
other secondary shadow, which veils, as it were, the shadow proper of the earth in
forms often indistinct and diffused, and modified by atmospherical phenomena, such
as clouds, haze, &c.
According to circumstances, the forms of this atmospheric shadow are variable in
each eclipse, being sometimes spherical, and at other times of very irregular curvatures.
The magnitude also of this shadow is extremely variable, on some observed occasions
extending over a space of three minutes of arc, as in the year 1772, on others of one
minute, as in 1773, and sometimes even less. The magnitude of the penumbra itself
is also subject to similar variations. It was observed to precede the nucleus of the
shadow from 2 to 10 minutes of time; in April, 1818, it even preceded the nucleus
by 15 minutes.
For 1856, when I (Hermann) had occasion to observe the moon's eclipse, no such
observations by others of the magnitude of the penumbra are known to me.
I found the magnitude of the penumbra equal to the semi-minor axis of the Mare
crisium. According to various observations, the shadow of the earth itself required
the following times for passing through the whole breadth of Mare crisium:
Observer. Time.
m s
Neumayr..................... 622
Niebour...................... 7 0
Riimker...................... 541
Schmidt...................... 7 10
Mean .... ." 6 34
Half the value of this time is 3m 17s, and this value of the magnitude of the
penumbra I adopted for the calculation of longitude from occupations of Tycho and
Mare crisium.