here. - Yale University

Understanding our Galaxy
The structure of our Milky Way Galaxy has been the main research
objective of the Yale Southern Observatory (YSO) since the founding of
the Cesco Observatory in 1962. Nearly five decades have been devoted
to improving and renovating the telescope, photographing the sky,
collecting and analyzing the data. We are now seeing the fruits of our
labors with the publication of the Yale-San Juan Southern Proper Motion
catalog (SPM4) of 103 million absolute proper motions of stars and
galaxies in the Southern Sky. The SPM4 is recognized as the premier
astrometric survey dedicated to the study of faint stars in our Galaxy and
it will remain so until the results from the next generation of space
satellites are available in approximately 2023.
From Telescope to Catalog
The 51-cm Double Astrograph
(below); Yale astronomer, Dr.
Terry Girard (top); and YSO
President Dr. William van
Altena (lower right) during the
installation of the CCD
cameras in 2000.
The SPM4 catalog is based on observations made with the YSO Double
Astrograph, the principal telescope of Cesco Observatory. The astrograph
consists of two lenses, each 51-cm in diameter; one designed to image blue
light and the other yellow light. From 1965 the lenses focused light
separately onto two photographic plates with dimensions of 43 x 43 cm,
and since 2000 onto two CCD cameras. The photographic plates were
purchased in the US, shipped to El Leoncito, where they were exposed in
the telescope, developed and then shipped back to the US for measurement
with the precision measuring machines at Yale and at the US Naval
Observatory. The CCD data were also analyzed at Yale, and combined
with the photographic measures to produce the catalog.
The Southern Sky as seen with the Double Astrograph photography in the
SPM4 catalog. The dark band in the image is the Milky Way disk, while
the two small dark spots at the bottom are the Large and Small
Magellanic Clouds.
Yale-UNSJ Collaboration
UNSJ and OAFA Argentine astronomer Lic. Carlos López with YSO
Chilean observer Danilo Castillo and Venezuelan astronomer and
SPM collaborator Dr. Katherine Vieira.
The SPM4 is the result of a 49-year collaboration between the YSO and the
Universidad Nacional de San Juan (UNSJ) – the longest agreement between
universities in Argentina and the United States. More than 50 scientific,
technical, administrative and support personnel from both countries as well as
others have participted in the research. The YSO has obtained $18.2 million
dollars (2011 dollars) in grant funds from various United States agencies,
including the NSF, NASA, Yale University, Columbia University and Ford
Foundation to build and operate the Cesco Observatory and to fund the SPM
program. Likewise, the UNSJ has contributed to the SPM through the
provision of scientific, technical and operations personnel as well as funds to
help support the Double Astrograph and the Cesco Observatory. To date, more
than 100 research papers documenting the results of the SPM have been
published in international research journals during the course of the program.
Yale astronomer, Dr. Dana Casetti prepares one of the SPM
photographic plates for measurement using the Yale PDS
microdensitometer.
SPM Future
After upgrades to the astrograph’s camera system in early 2011, SPM
observations continued with the objective of extending the sky coverage
of the SPM4 catalog as well as improving its precision for targets of
special interest. The broad goals of the SPM are to improve our
understanding of the kinematical and spatial structure of our Milky Way
Galaxy through observations made with the Double Astrograph.
The SPM Program and the Yale Southern Observatory