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| Landolt standard stars | |
|---|---|
| Name | Landolt standard stars |
| Type | Photometric standard star network |
| Established | 1973 |
| Creator | Arlo U. Landolt |
| Wavelength | Optical (UBVRI) |
| Purpose | Photometric calibration |
Landolt standard stars
The Landolt standard stars are a widely used network of optical photometric standard stars established to provide calibrated magnitudes and colors for astronomical photometry. They serve as reference points for calibrating instruments and datasets from observatories, telescopes, and missions, enabling consistent comparison of photometric measurements across projects and epochs. The network underpins much optical astronomy by linking instrumental measurements to a common magnitude system.
Arlo U. Landolt compiled precise photometric measurements that anchor the Johnson–Morgan photometric system, the UBV system, and extensions into the Cousins photometric system for use by observers at facilities such as the Kitt Peak National Observatory, the Cerro Tololo Inter-American Observatory, and the European Southern Observatory. The standards are routinely used by teams operating instruments on the Hubble Space Telescope, the Very Large Telescope, the Subaru Telescope, and survey projects that require cross-calibration with historical datasets from the Palomar Observatory and the Mount Wilson Observatory.
The initial catalogs were published in the 1970s by Arlo U. Landolt while affiliated with institutions including the University of Arizona and observations taken at sites like the Kitt Peak National Observatory. Subsequent expansions addressed needs raised by programs led at observatories such as the Cerro Tololo Inter-American Observatory and collaborative efforts involving researchers associated with the Royal Observatory, Edinburgh and the Harvard College Observatory. The development responded to the evolution of photometric systems from the early work of Harold Johnson and William Morgan through refinements influenced by researchers at the South African Astronomical Observatory and instrument teams at the Space Telescope Science Institute.
Landolt observations adopt passbands tied to the classical UBVRI system, relating to filter profiles used at facilities like the Kitt Peak National Observatory and instruments on the Hubble Space Telescope and the Very Large Telescope. Photometric reductions reference atmospheric extinction measurements taken at sites including the Cerro Tololo Inter-American Observatory and employ transformations connecting to systems defined by figures such as A. W. J. Cousins and historical standards from the Harvard College Observatory and Mount Stromlo Observatory. Observers cross-match Landolt stars with catalogs produced by missions like Hipparcos and analyses performed by groups at the European Southern Observatory.
Landolt’s foundational papers published in journals and conference proceedings are central references used by teams at the Space Telescope Science Institute, the National Optical Astronomy Observatory, and researchers linked to the University of Arizona. Major releases expanded the list of equatorial standards and included precise UBVRI magnitudes for fields used by projects run from the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The catalogs are cited in work from groups at the European Southern Observatory, the California Institute of Technology, and the Massachusetts Institute of Technology that require stable photometric references.
Calibration with Landolt stars typically involves observing sequences during photometric nights at facilities such as the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory, deriving zero points and color terms for instruments akin to those on the Hubble Space Telescope or the Very Large Telescope. Procedures incorporate atmospheric extinction coefficients measured at sites including Mauna Kea and cross-calibration with space-borne catalogs like Hipparcos and datasets from the Sloan Digital Sky Survey teams. Observing strategies are practiced by research groups at the National Optical Astronomy Observatory and taught in courses at the University of Arizona and Princeton University.
The Landolt network provides photometric stability for many applications, but limitations arise from transformations between filter systems used at observatories like the Cerro Tololo Inter-American Observatory, nonlinearity in detectors employed at facilities including the Subaru Telescope, and atmospheric variability at sites such as Mauna Kea. Updates and supplementary standards have been produced to address sparse sky coverage and faint-end calibration needs by researchers at the European Southern Observatory, the Space Telescope Science Institute, and university groups at the University of Cambridge and the California Institute of Technology.
Landolt standards underpin photometric calibration in studies conducted with telescopes like the Hubble Space Telescope, the Very Large Telescope, and the Subaru Telescope, enabling consistent photometry across campaigns led by teams at the Space Telescope Science Institute, the European Southern Observatory, and the National Optical Astronomy Observatory. They have been essential to programs ranging from variable star work by groups at the Harvard College Observatory to supernova cosmology collaborations that include researchers from the California Institute of Technology and the Princeton University. The network’s role in tying ground-based photometry to established systems has influenced survey projects connected to the Sloan Digital Sky Survey, the Gaia mission, and legacy datasets handled by the European Space Agency.
Category:Astronomical catalogues