146
7 Star Streams
out by Williamina Paton Stevens Fleming (1857–1911). It was a preliminary
study and Edward Pickering and his female assistants, often referred to as
‘Pickerings harem’, among which Antonia Caetana de Paiva Pereira Maury
(1866–1952) and Annie Jump Cannon (1863–1941), completed the catalog
and in the course of that defined in an elaborate classification system, the
Harvard classifications . The Henry Draper Catalog and supplements, published
between 1918 and 1936, are still in use today.
Edward Pickering had also given a presentation during the congress in St.
Louis and Kapteyn undoubtedly spoke extensively with him and made him
enthusiastic about his Plan. The Harvard College Observatory also operated
a southern observatory, the Boyden Station in Peru, first located near Lima,
later inland near Arequipa. It was built with money from engineer and inventor Uriah Atherton Boyden (1804–1879). Edward Pickering finally pledged
his cooperation to Kapteyn and agreed that all Selected Areas would be photographed with his telescopes on both hemispheres.
But Kapteyn had to pay a price. Edward Pickering wanted something to be
added to the Plan, namely that there would be more Select Area’s spread across
the Milky Way, especially in areas where star-density was high or where there
were specific nebulae. That would provide more information about the Milky
Way, and provide better sampling. Kapteyn resisted this addition because of
the extra work and time it would take, but eventually he had to agree to keep
Pickering on board. Pickering then set to work energetically, and all plates had
been recorded in 1914. Kapteyn and his people set about measuring those
plates. Eventually the results of this Harvard-Groningen Durchmusterung were
published in three volumes in the Annals of the Harvard College Observatory,
in 1918, 1923 and again 1923, the last two as far as Kapteyn was concerned
posthumously. The results of the Special Plan were published only in 1952,
under the direction of Kapteyn’s successor Pieter van Rhijn.
George Hale had founded the Yerkes Observatory near Chicago in 1897 with
money from the broker and financier Charles Tyson Yerkes (1837–1905). Hale
soon built the largest refractor telescope in the world. A refractor telescope has
a lens at the top of the tube as the primary optical element, in contrast to a
reflector, which has a mirror at the bottom. A lens has the disadvantage, unlike
a mirror, that it can only be supported at the edges. This means that it deforms
when the orientation of the telescope changes. Furthermore, the light must
pass through the glass of the lens, partially absorbing it. A mirror reflects, and
although some of the light is always lost, that loss is minimal if the mirror is kept
clean. In modern telescopes, a thin layer of aluminum (in some cases silver) is
applied to the mirror by atomization in a vacuum chamber. Breaking of light
through a lens, as opposed to reflection, also depends on the wavelength. Blue
7 Star Streams
out by Williamina Paton Stevens Fleming (1857–1911). It was a preliminary
study and Edward Pickering and his female assistants, often referred to as
‘Pickerings harem’, among which Antonia Caetana de Paiva Pereira Maury
(1866–1952) and Annie Jump Cannon (1863–1941), completed the catalog
and in the course of that defined in an elaborate classification system, the
Harvard classifications . The Henry Draper Catalog and supplements, published
between 1918 and 1936, are still in use today.
Edward Pickering had also given a presentation during the congress in St.
Louis and Kapteyn undoubtedly spoke extensively with him and made him
enthusiastic about his Plan. The Harvard College Observatory also operated
a southern observatory, the Boyden Station in Peru, first located near Lima,
later inland near Arequipa. It was built with money from engineer and inventor Uriah Atherton Boyden (1804–1879). Edward Pickering finally pledged
his cooperation to Kapteyn and agreed that all Selected Areas would be photographed with his telescopes on both hemispheres.
But Kapteyn had to pay a price. Edward Pickering wanted something to be
added to the Plan, namely that there would be more Select Area’s spread across
the Milky Way, especially in areas where star-density was high or where there
were specific nebulae. That would provide more information about the Milky
Way, and provide better sampling. Kapteyn resisted this addition because of
the extra work and time it would take, but eventually he had to agree to keep
Pickering on board. Pickering then set to work energetically, and all plates had
been recorded in 1914. Kapteyn and his people set about measuring those
plates. Eventually the results of this Harvard-Groningen Durchmusterung were
published in three volumes in the Annals of the Harvard College Observatory,
in 1918, 1923 and again 1923, the last two as far as Kapteyn was concerned
posthumously. The results of the Special Plan were published only in 1952,
under the direction of Kapteyn’s successor Pieter van Rhijn.
George Hale had founded the Yerkes Observatory near Chicago in 1897 with
money from the broker and financier Charles Tyson Yerkes (1837–1905). Hale
soon built the largest refractor telescope in the world. A refractor telescope has
a lens at the top of the tube as the primary optical element, in contrast to a
reflector, which has a mirror at the bottom. A lens has the disadvantage, unlike
a mirror, that it can only be supported at the edges. This means that it deforms
when the orientation of the telescope changes. Furthermore, the light must
pass through the glass of the lens, partially absorbing it. A mirror reflects, and
although some of the light is always lost, that loss is minimal if the mirror is kept
clean. In modern telescopes, a thin layer of aluminum (in some cases silver) is
applied to the mirror by atomization in a vacuum chamber. Breaking of light
through a lens, as opposed to reflection, also depends on the wavelength. Blue