142
7 Star Streams
stars across the entire sky. But to significantly fainter magnitudes than available
in the existing star catalogs. He defined for this his Plan of Selected Areas. In
essence, he selected a limited number of small areas all over the entire sky,
which would allow a representative census of the stars to be determined. In the
end it resulted in 206 uniformly distributed areas. To produce an inventory
of stars in these areas was a gigantic undertaking and in order to complete
it successfully, he needed the cooperation of a large number of observatories,
especially those with the best telescopes and instruments. It takes tact (and
time) to accomplish such a thing.
Kapteyn began discussing his plan with many astronomers. His visit to St.
Louis also played an important role in that respect; the directors of the most
important American observatories—as well as some others—were there and
Kapteyn must have talked to them about his plans. After returning to Groningen, he wrote a draft of the Plan, which circulated for several years among
astronomers and directors of observatories. The matter must also have been
the subject of much deliberation when a year after St. Louis, in 1905, he visited
South Africa—the only trip he would ever make to the southern hemisphere in
his lifetime. It had been Kapteyn’s old wish to visit David Gill (see Fig. 7.13) in
his own surroundings and to see the southern starry sky, which he had after all
mapped out with him. The occasion was a meeting of the British Association for
the Advancement of Science, that would meet in Cape Town and Kapteyn had
been invited to that meeting. This organization, now called the British Association, was founded in 1831 with the aim of promoting knowledge about science
and to foster the interaction between scientists. The Association met once a
year. I quote again from Henriette Hertzsprung–Kapteyn’s biography [1]:
In the summer of that year Kapteyn traveled to South Africa, at the invitation
of the British Association, which held its large international meeting there. De
Sitter, who was then his assistant, accompanied him. Several other astronomers
traveled also along with him on the same ship: Backlund, director of the Pulkovo
observatorium (Russia), Donner, Hinks and Cookson, the latter both English
astronomers. They talked a lot during the trip and founded ‘The Astronomical
Society of the Atlantic’ for the duration of the sea voyage. The main topic of
their discussions probably was the Plan of Selected Areas, of which each of them
had brought a copy of the draft. Hinks made notes of what was proposed, and
Kapteyn could be satisfied with the results of the discussions. Everyone wanted
their part in the work. In South Africa he was able to win even more participants
for his plans.
For a long time it had been his wish to see Gill in his own observatory, because
one only gets to know a man completely when one meets him in his working
place. With pride he was shown the observatory, which Gill had brought so much
7 Star Streams
stars across the entire sky. But to significantly fainter magnitudes than available
in the existing star catalogs. He defined for this his Plan of Selected Areas. In
essence, he selected a limited number of small areas all over the entire sky,
which would allow a representative census of the stars to be determined. In the
end it resulted in 206 uniformly distributed areas. To produce an inventory
of stars in these areas was a gigantic undertaking and in order to complete
it successfully, he needed the cooperation of a large number of observatories,
especially those with the best telescopes and instruments. It takes tact (and
time) to accomplish such a thing.
Kapteyn began discussing his plan with many astronomers. His visit to St.
Louis also played an important role in that respect; the directors of the most
important American observatories—as well as some others—were there and
Kapteyn must have talked to them about his plans. After returning to Groningen, he wrote a draft of the Plan, which circulated for several years among
astronomers and directors of observatories. The matter must also have been
the subject of much deliberation when a year after St. Louis, in 1905, he visited
South Africa—the only trip he would ever make to the southern hemisphere in
his lifetime. It had been Kapteyn’s old wish to visit David Gill (see Fig. 7.13) in
his own surroundings and to see the southern starry sky, which he had after all
mapped out with him. The occasion was a meeting of the British Association for
the Advancement of Science, that would meet in Cape Town and Kapteyn had
been invited to that meeting. This organization, now called the British Association, was founded in 1831 with the aim of promoting knowledge about science
and to foster the interaction between scientists. The Association met once a
year. I quote again from Henriette Hertzsprung–Kapteyn’s biography [1]:
In the summer of that year Kapteyn traveled to South Africa, at the invitation
of the British Association, which held its large international meeting there. De
Sitter, who was then his assistant, accompanied him. Several other astronomers
traveled also along with him on the same ship: Backlund, director of the Pulkovo
observatorium (Russia), Donner, Hinks and Cookson, the latter both English
astronomers. They talked a lot during the trip and founded ‘The Astronomical
Society of the Atlantic’ for the duration of the sea voyage. The main topic of
their discussions probably was the Plan of Selected Areas, of which each of them
had brought a copy of the draft. Hinks made notes of what was proposed, and
Kapteyn could be satisfied with the results of the discussions. Everyone wanted
their part in the work. In South Africa he was able to win even more participants
for his plans.
For a long time it had been his wish to see Gill in his own observatory, because
one only gets to know a man completely when one meets him in his working
place. With pride he was shown the observatory, which Gill had brought so much