9.7 Results of the Visits to Mount Wilson
197
so-called North Polar Sequence (of standard stars) on the same plate. This was
done with a smaller telescope of 10 in. aperture, because it was only necessary
to record the brightest stars. This part of the work was done by Milton Lasell
Humason (1891–1972).
A total of more than a thousand plates had been taken. The deep 60 in.
plates were copied in Pasadena and then sent to Groningen. There Kapteyn had
arranged for assistants and calculators to measure the plates. These were largely
paid for by the Carnegie Institution. The support of the University of Groningen for Kapteyn and his pioneering work was again far from overwhelming,
although at that time he was definitely their greatest and most famous scholar.
Kapteyn did not live to see the completion of the work. Thanks to the unceasing efforts of Seares and Kapteyn’s successor in Groningen Pieter van Rhijn, the
Mount Wilson Catalog of photographic magnitudes in Selected Areas 1–139 was
published in 1930 as a special publication by the Carnegie Institution, eight
years after Kapteyn’s death. Of course, Kapteyn did see preliminary results.
An important consequence of Kapteyn’s association with the Carnegie Institution and Mount Wilson Observatory was the introduction to America of
young astronomers from the Netherlands and some other European countries.
American astronomy was on the rise, observatories were built or expanded,
and there was always a need for promising, talented young astronomers; so
many positions, temporary or permanent, were available. Kapteyn opened
a veritable ‘pipeline’, as the American astronomy historian David DeVorkin
called it. Arnold Ernst Kohlschütter (1883–1969), Adriaan van Maanen, Ejnar
Hertzsprung and Pieter van Rhijn, among others, profited from this.
Kohlschütter was a student of Karl Schwarzschild in Potsdam, with whom
Kapteyn maintained good ties. He had obtained his PhD in Göttingen when
Schwarzschild was still teaching there and now worked at the Bergedorfer
Sternwarte near Hamburg. At Schwarzschild’s request Kapteyn wrote a very
strong recommendation to George Hale to arrange a visit from Kohlschütter.
He left the same year and worked for a number of years with staff member
Walter Adams. We will meet him again later.
Van Maanen was actually a student of Albertus Nijland in Utrecht. As we
already saw, Adriaan van Maanen worked for some time in Groningen with
Kapteyn and considered himself to be a student of Kapteyn rather than Nijland.
His PhD thesis from 1911 was about proper motions of stars in the h and χ
Persei clusters (see Fig. 7.10). Van Maanen was fortunate to have a rich cousin,
who made it possible financially to volunteer to work at the Yerkes observatory
for some time. He was personally delivered there by Kapteyn in 1911, when
the latter was on his way to Mount Wilson. After that period Adriaan van
Maanen went, no doubt with a strong recommendation from Kapteyn, to
197
so-called North Polar Sequence (of standard stars) on the same plate. This was
done with a smaller telescope of 10 in. aperture, because it was only necessary
to record the brightest stars. This part of the work was done by Milton Lasell
Humason (1891–1972).
A total of more than a thousand plates had been taken. The deep 60 in.
plates were copied in Pasadena and then sent to Groningen. There Kapteyn had
arranged for assistants and calculators to measure the plates. These were largely
paid for by the Carnegie Institution. The support of the University of Groningen for Kapteyn and his pioneering work was again far from overwhelming,
although at that time he was definitely their greatest and most famous scholar.
Kapteyn did not live to see the completion of the work. Thanks to the unceasing efforts of Seares and Kapteyn’s successor in Groningen Pieter van Rhijn, the
Mount Wilson Catalog of photographic magnitudes in Selected Areas 1–139 was
published in 1930 as a special publication by the Carnegie Institution, eight
years after Kapteyn’s death. Of course, Kapteyn did see preliminary results.
An important consequence of Kapteyn’s association with the Carnegie Institution and Mount Wilson Observatory was the introduction to America of
young astronomers from the Netherlands and some other European countries.
American astronomy was on the rise, observatories were built or expanded,
and there was always a need for promising, talented young astronomers; so
many positions, temporary or permanent, were available. Kapteyn opened
a veritable ‘pipeline’, as the American astronomy historian David DeVorkin
called it. Arnold Ernst Kohlschütter (1883–1969), Adriaan van Maanen, Ejnar
Hertzsprung and Pieter van Rhijn, among others, profited from this.
Kohlschütter was a student of Karl Schwarzschild in Potsdam, with whom
Kapteyn maintained good ties. He had obtained his PhD in Göttingen when
Schwarzschild was still teaching there and now worked at the Bergedorfer
Sternwarte near Hamburg. At Schwarzschild’s request Kapteyn wrote a very
strong recommendation to George Hale to arrange a visit from Kohlschütter.
He left the same year and worked for a number of years with staff member
Walter Adams. We will meet him again later.
Van Maanen was actually a student of Albertus Nijland in Utrecht. As we
already saw, Adriaan van Maanen worked for some time in Groningen with
Kapteyn and considered himself to be a student of Kapteyn rather than Nijland.
His PhD thesis from 1911 was about proper motions of stars in the h and χ
Persei clusters (see Fig. 7.10). Van Maanen was fortunate to have a rich cousin,
who made it possible financially to volunteer to work at the Yerkes observatory
for some time. He was personally delivered there by Kapteyn in 1911, when
the latter was on his way to Mount Wilson. After that period Adriaan van
Maanen went, no doubt with a strong recommendation from Kapteyn, to