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| DAOPHOT | |
|---|---|
| Name | DAOPHOT |
| Released | 1987 |
| Developer | Stetson Observatory / Mount Hopkins / Kitt Peak |
| Programming language | Fortran |
| Operating system | Unix / VMS |
| License | Proprietary (historical) |
DAOPHOT DAOPHOT is a software package for stellar photometry designed to extract point-spread-function photometry from crowded astronomical images. It provides tools for source detection, point-spread-function modeling, profile fitting, and aperture corrections, and has been widely used in observational programs associated with major observatories and surveys. DAOPHOT influenced pipelines at institutions and missions that include ground-based telescopes and space observatories.
DAOPHOT automates the measurement of stellar magnitudes and positions in densely populated fields, addressing issues encountered in images from facilities such as Kitt Peak National Observatory, Mount Hopkins Observatory, Cerro Tololo Inter-American Observatory, Palomar Observatory, and European Southern Observatory. Its workflow integrates detection, point-spread-function construction, iterative subtraction, and magnitude calibration used in projects tied to Harvard-Smithsonian Center for Astrophysics, Space Telescope Science Institute, National Optical Astronomy Observatory, Max Planck Institute for Astronomy, and California Institute of Technology. The package was applied in programs associated with instruments on Hale Telescope, Hubble Space Telescope, Subaru Telescope, Very Large Telescope, and Keck Observatory.
DAOPHOT was developed in the mid-1980s by Peter Stetson at Dominion Astrophysical Observatory/Stetson Observatory with deployment contexts at Mount Hopkins and Kitt Peak. Early adopters included research groups at Harvard University, Yale University, University of Toronto, University of Cambridge, and Princeton University. It became a standard tool for observational campaigns such as those led by teams at Carnegie Institution for Science, Jet Propulsion Laboratory, European Southern Observatory, and national facilities including NOAO and NASA. The software’s dissemination influenced survey projects at Sloan Digital Sky Survey, Two Micron All Sky Survey, Microlensing Observations in Astrophysics, and time-domain programs associated with Palomar Transient Factory and Zwicky Transient Facility.
DAOPHOT’s methodology centers on empirical point-spread-function fitting, iterative source subtraction, and weighted least-squares optimization applied to pixel data from detectors used at Kitt Peak National Observatory, Cerro Tololo, and Mauna Kea Observatories. The package implements analytic PSF models combined with lookup tables to capture variations across frames, incorporating adjustments relevant to instruments on Hubble Space Telescope’s Wide Field Planetary Camera, Advanced Camera for Surveys, and ground-based detectors at Keck Observatory and Subaru Telescope. Its source detection routines complement astrometric solutions used in catalogs like Hipparcos, Tycho, and Gaia through cross-matching and photometric calibration strategies developed with standards from Landolt, Stetson Photometric Standards, and observatory programs at Cerro Tololo Inter-American Observatory.
Originally implemented in Fortran for systems such as VAX/VMS and Unix workstations common at National Optical Astronomy Observatory and university departments, DAOPHOT was distributed alongside companion tools and scripts used at STScI and in professional observatories. Modifications and wrappers were created to interface with IRAF packages maintained at NOAO IRAF, integration efforts for pipelines at Space Telescope Science Institute, and later conversions for use in environments associated with Astropy and community tools developed by groups at University of California, Smithsonian Astrophysical Observatory, and Max Planck Society. Successor utilities, utilities for crowded-field photometry, and community ports were influenced by software from IDL Astronomy User's Library, SExtractor authors at Observatoire de Marseille, and pipeline teams at European Southern Observatory.
DAOPHOT was applied to studies of star clusters observed at Mount Wilson Observatory, Roque de los Muchachos Observatory, and La Silla Observatory, variable-star surveys at Cerro Tololo Inter-American Observatory, microlensing campaigns operated by consortia including OGLE and MOA, and follow-up photometry for transit surveys connected to Kepler, CoRoT, and ground-based transit programs at Palomar Observatory. It supported analyses in stellar population research carried out at University of Cambridge, University of Chicago, University of California, Berkeley, University of Michigan, and space mission teams at NASA centers. DAOPHOT’s outputs were integrated into catalogs and legacy datasets curated by institutions such as Centre de Données astronomiques de Strasbourg and archives at Space Telescope Science Institute.
DAOPHOT excels in crowded-field precision photometry for images taken with classical CCDs and early mosaic detectors used at Kitt Peak National Observatory and Cerro Tololo. Its limitations include performance bottlenecks on very large-format detectors developed at Lawrence Berkeley National Laboratory projects and reduced efficiency for wide-field survey cameras employed by Sloan Digital Sky Survey and Pan-STARRS without substantial pipeline adaptation. Challenges arise with highly undersampled data from instruments aboard Hubble Space Telescope pre-repair epochs and with treatment of complex backgrounds in regions like Galactic Center observations performed at Keck Observatory and Very Large Telescope. Users at institutions such as University of Hawaii and Arizona State University have combined DAOPHOT logic with modern computing frameworks to mitigate these constraints.
DAOPHOT’s concepts—empirical PSF modeling, iterative subtraction, and precision fitting—directly influenced software developed at European Southern Observatory, Space Telescope Science Institute, Astropy Project, NOAO, and teams behind SExtractor, DoPHOT, ALLFRAME, and modern photometric packages used in pipelines for LSST, Rubin Observatory, Zwicky Transient Facility, and mission archives managed by NASA and ESA. Academic programs at Harvard-Smithsonian Center for Astrophysics, Princeton University, Caltech, and Max Planck Institute for Astronomy incorporated DAOPHOT-derived techniques into curricula and toolchains. Its role in enabling precise photometry contributed to discoveries recognized by awards and collaborations associated with institutions such as Royal Astronomical Society, American Astronomical Society, and national space agencies.
Category:Astronomical software