DASCH | |
---|---|
Commercial? | No |
Location | Cambridge, Massachusetts, United States |
Owner | Center for Astrophysics | Harvard & Smithsonian |
Founder | Jonathan E. Grindlay, principal investigator |
Established | 2001 |
Funding | National Science Foundation |
Status | Active |
Website | dasch.rc.fas.harvard.edu |
The Digital Access to a Sky Century @ Harvard (DASCH) is a project to preserve and digitize images recorded on astronomical photographic plates created before astronomy became dominated by digital imaging. It is a major project of the Center for Astrophysics | Harvard & Smithsonian. Over 500,000 glass plates held by the Harvard College Observatory are to be digitized. [1] The digital images will contribute to time domain astronomy, providing over a hundred years of data that may be compared to current observations.
From 1885 until 1992, the Harvard College Observatory repeatedly photographed the night sky using observatories in both the northern and southern hemispheres. Over half a million glass photographic plates are stored in the observatory archives providing a unique resource to astronomers. The Harvard collection is over three times the size of the next largest collection of astronomical photographic plates and is almost a quarter of all known photographic images of the sky on glass plates. Those plates were seldom used after digital imaging became the standard near the end of the twentieth century. [2] The scope of the Harvard plate collection is unique in that it covers the entire sky for a very long period of time.
The project web site states that the goals of DASCH are to
enable new Time Domain Astronomy (TDA) science, including:
- Conduct the first long-term temporal variability survey on days to decades time scales
- Novae and dwarf novae distributions and populations in the Galaxy
- Black hole and neutron star X-ray binaries in outburst: constraining the BH, NS binary populations in the Galaxy
- Black hole masses of bright quasars from long-term variability measures to constrain their characteristic shortest timescales and thus size
- Quiescent black holes in galactic nuclei revealed by tidal disruption of a passing field star and resultant optical flare
- Unexpected classes of variables or temporal behavior of known objects: preview of what PanSTARSS and LSST may see in much more detail but on shorter timescales. [3]
Digitizing the Harvard College Observatory's astronomical plates archive was first considered in the 1980s by Jonathan E. Grindlay, a professor of astronomy at Harvard. Grindlay encouraged Alison Doane, then curator of the archive, to explore digitizing the collection with a commercial image scanner. Working with Jessica Mink, an archivist of the Center for Astrophysics | Harvard & Smithsonian, Grindlay and Doane determined that a commercial scanner could produce suitable digital images but also found that such machines were too slow. [4] Working full-time, it would have taken over 50 years to digitize the plates in the Harvard archive with commercial scanners. [5]
Doane presented a talk about the problem at a meeting of the Amateur Telescope Makers of Boston whose clubhouse is located on the grounds of MIT's Haystack Observatory. Bob Simcoe, a club member and retired engineer, volunteered to help design a machine suitable for the task. The machine needed to position and record the stellar images on the plates to within half a micron and account for different emulsions, plate thicknesses and densities, exposure times, processing methods and so on. Software was developed by Mink, Edward Los, another volunteer from the club, and Silas Laycock, a researcher. Thanks to a grant from the National Science Foundation and donations of time and material, creation of the scanner began in 2004. The scanner was completed and tested in 2006. Over 500 plates were imaged before the project ran out of money in July 2007. [5]
For the digital images to be useful for research, the associated metadata also needs to be digitalized. That data describes what part of the sky and what objects were recorded on each plate along with date, time, telescope, and other pertinent information. The metadata is recorded in about 1,200 logbooks and on the card catalog of the collection. In addition, each plate is stored in a paper jacket that includes related information and often scientifically and historically important notes left by previous researchers, including notable astronomers such as Henrietta Swan Leavitt and Annie Jump Cannon. George Champine, another volunteer from the Amateur Telescope Makers of Boston, photographed the logbooks. The paper jacket for each plate is photographed as each plate is cleaned and imaged. [5]
The first plate images were created by Harvard Observatory staff members in the winter of 2001–2002 using commercial scanners. A larger test that included imaging 100 plates was conducted in the summer of 2002. Those tests indicated that commercially available scanners were too slow for digitizing the Harvard plate collection and motivated the development of a custom-built scanner. The test images are available on-line. [6] The custom-built high-speed scanner was completed and tested in 2006. [4]
Improvement of the scanner and associated software continues. A failure of a single part in the plate loader led to a breakdown of the scanner in August 2014. A new plate loader control system was designed and built by Bob Simcoe allowing scanning to resume in November 2014. [7]
As of November 2014 [update] , over 80,000 plates have been scanned and the data released on the DASCH web site, approximately 6.5 percent of the plate collection. The 80,000th plate was scanned on November 13, 2014. [7]
Most of the metadata for the plate collection is contained in 663 bound volumes and about 500 looseleaf logbooks. Photographs of all of the logbook pages are available on the DASCH website. The effort to digitize this information began at Harvard. Some was done in India. The effort later moved to the American Museum of Natural History where volunteers worked under the supervision of Dr Michael Shara, Curator of the Department of Astrophysics and Holly Klug, Department. of Volunteer Services. [8]
In August 2014, the transcription of the Harvard plate logbooks was taken over by the Smithsonian Transcription Center, a new program to recruit volunteers to transcribe historical documents. This citizen science project is ongoing with a goal of completing all of the transcription before 2017. [2]
The DASCH will not generally accept special requests for scanning a particular part of the sky from the collection so that the digitization progresses efficiently. The DASCH team did accommodate two special requests to image plates that were not part of the Harvard collection "for scientifically compelling reasons". [7]
The New Horizons team requested images of Pluto in order to improve the dwarf planet's ephemeris that was needed to plan precise adjustments to the spacecraft's trajectory. DASCH scanned 843 plates showing Pluto that were taken by the 40 inch telescope at Lowell Observatory from 1930 to 1951. [7]
Forty-two plates of the Cassiopeia A supernova remnant taken by the Hale telescope at the Palomar Observatory from 1951 to 1989 were imaged to support a study comparing x-ray and visual emissions. [7] As of November 2014 [update] , the study has not been published in a peer reviewed journal. [9]
Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography. Besides being able to record the details of extended objects such as the Moon, Sun, and planets, modern astrophotography has the ability to image objects invisible to the human eye such as dim stars, nebulae, and galaxies. This is done by long time exposure since both film and digital cameras can accumulate and sum photons over these long periods of time.
Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinner than common window glass.
The Adler Planetarium is a public museum in Chicago, Illinois, dedicated to astronomy and astrophysics. It was founded in 1930 by local businessman Max Adler. Located on the northeastern tip of Northerly Island on Lake Michigan in the city, the Adler Planetarium was the first planetarium in the United States. It is part of Chicago's Museum Campus, which includes the John G. Shedd Aquarium and The Field Museum. The Planetarium's mission is to inspire exploration and understanding of the universe.
Williamina Paton Stevens Fleming was a Scottish astronomer active in the United States. During her career, she helped develop a common designation system for stars and cataloged thousands of stars and other astronomical phenomena. Among several career achievements that advanced astronomy, Fleming is noted for her discovery of the Horsehead Nebula in 1888.
Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observatory is granted to Caltech and its research partners, which include the Jet Propulsion Laboratory (JPL), Yale University, and the National Optical Observatories of China.
The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United States, and was founded in 1839. With the Smithsonian Astrophysical Observatory, it forms part of the Center for Astrophysics | Harvard & Smithsonian.
The Cerro Tololo Inter-American Observatory (CTIO) is an astronomical observatory located on Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Cerro Pachón about 10 kilometres (6.2 mi) to the southeast. It is approximately 80 kilometres (50 mi) east of La Serena, where support facilities are located. The site was identified by a team of scientists from Chile and the United States in 1959, and it was selected in 1962. Construction began in 1963 and regular astronomical observations commenced in 1965. Construction of large buildings on Cerro Tololo ended with the completion of the Víctor Blanco Telescope in 1974, but smaller facilities have been built since then. Cerro Pachón is still under development, with two large telescopes inaugurated since 2000, and one in the early stages of construction
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 and was named after the Alfred P. Sloan Foundation, which contributed significant funding.
The National Geographic Society – Palomar Observatory Sky Survey was a major astronomical survey, that took almost 2,000 photographic plates of the night sky. It was conducted at Palomar Observatory, California, United States, and completed by the end of 1958.
The Digitized Sky Survey (DSS) is a digitized version of several photographic astronomical surveys of the night sky, produced by the Space Telescope Science Institute between 1983 and 2006.
The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope under construction, as part of the US Extremely Large Telescope Program (US-ELTP), as of 2022. It will consist of seven 8.4 m (27.6 ft) diameter primary segments, that will observe optical and near infrared (320–25000 nm) light, with the resolving power of a 24.5 m (80.4 ft) primary mirror and collecting area equivalent to a 22.0 m (72.2 ft) one, which is about 368 square meters. The telescope is expected to have a resolving power 10 times that of the Hubble Space Telescope and four times that of the James Webb Space Telescope, although it will be unable to image in the same infrared frequencies available to telescopes in space. As of May 2021, six mirrors have been cast and the construction of the summit facility has begun.
The Center for Astrophysics | Harvard & Smithsonian (CfA), alternatively called the Harvard–Smithsonian Center for Astrophysics, is an astrophysics research institute jointly operated by the Harvard College Observatory and Smithsonian Astrophysical Observatory. Founded in 1973 and headquartered in Cambridge, Massachusetts, the CfA leads a broad program of research in astronomy, astrophysics, Earth and space sciences, as well as science education. The CfA either leads or participates in the development and operations of more than fifteen ground- and space-based astronomical research observatories across the electromagnetic spectrum, including the forthcoming Giant Magellan Telescope (GMT) and the Chandra X-ray Observatory, one of NASA's Great Observatories.
The UK Schmidt Telescope (UKST) is a 1.24 metre Schmidt telescope operated by the Australian Astronomical Observatory ; it is located adjacent to the 3.9 metre Anglo-Australian Telescope at Siding Spring Observatory, Australia. It is very similar to the Samuel Oschin telescope in California. The telescope can detect objects down to magnitude 21 after an hour of exposure on photographic plates.
An astronomical survey is a general map or image of a region of the sky that lacks a specific observational target. Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of objects that share a common type or feature. Surveys are often restricted to one band of the electromagnetic spectrum due to instrumental limitations, although multiwavelength surveys can be made by using multiple detectors, each sensitive to a different bandwidth.
The Calar Alto Observatory is an astronomical observatory located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in the Sierra de Los Filabres range.
The Vera C. Rubin Observatory, previously referred to as the Large Synoptic Survey Telescope (LSST), is an astronomical observatory currently under construction in Chile. Its main task will be carrying out a synoptic astronomical survey, the Legacy Survey of Space and Time (LSST). The word synoptic is derived from the Greek words σύν and ὄψις, and describes observations that give a broad view of a subject at a particular time. The observatory is located on the El Peñón peak of Cerro Pachón, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes. The LSST Base Facility is located about 100 kilometres (62 mi) away by road, in the town of La Serena. The observatory is named for Vera Rubin, an American astronomer who pioneered discoveries about galaxy rotation rates.
An integral field spectrograph, or a spectrograph equipped with an integral field unit (IFU), is an optical instrument combining spectrographic and imaging capabilities, used to obtain spatially resolved spectra in astronomy and other fields of research such as bio-medical science and Earth observation.
BICEP and the Keck Array are a series of cosmic microwave background (CMB) experiments. They aim to measure the polarization of the CMB; in particular, measuring the B-mode of the CMB. The experiments have had five generations of instrumentation, consisting of BICEP1, BICEP2, the Keck Array, BICEP3, and the BICEP Array. The Keck Array started observations in 2012 and BICEP3 has been fully operational since May 2016, with the BICEP Array beginning installation in 2017/18.
Time-domain astronomy is the study of how astronomical objects change with time. Though the study may be said to begin with Galileo's Letters on Sunspots, the term now refers especially to variable objects beyond the Solar System. This may be due to movement or changes in the object itself. Common targets included are supernovae, pulsating stars, novas, flare stars, blazars and active galactic nuclei. Visible light time domain studies include OGLE, HAT-South, PanSTARRS, SkyMapper, ASAS, WASP, CRTS, and in a near future the LSST at the Vera C. Rubin Observatory.
Giovanni Fazio is an American physicist at Center for Astrophysics | Harvard & Smithsonian. He is an astrophysicist who has initiated and participated in multiple observation programs.