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SDSS Web Services
Tamás Budavári Johns Hopkins University
Coding against the UniverseCoding against the Universe
SC4DEVO-1 Tamás Budavári (JHU) 2
Outline
SDSS Primer
Technology
Web ServicesData Access
• Images• Spectra• Catalog
Higher Level
SC4DEVO-1 Tamás Budavári (JHU) 3
SDSS Imaging Survey
2.5m telescopeApache Point, NM5 photometric bandsDrift scan operation
Photo pipeline100,000,000 galaxiesAutomated reductionCatalog archive server
SC4DEVO-1 Tamás Budavári (JHU) 7
SDSS Spectropscopy
Two spectrographsRed and blue part
Optical fibers
640 in each bundle
Plugged manually
Automatic reduction
2D and 1D pipelines
Catalog archive server
SC4DEVO-1 Tamás Budavári (JHU) 9
Developing Web Services
We chose the .NET FrameworkThe C# programming languageExtensive class library (for free)Simple and efficient database accessFast imaging and graphics routinesRapid development in Visual StudioVery easy Web Services programming
Use CVS for versioning
SC4DEVO-1 Tamás Budavári (JHU) 10
Custom Tools and Packages
Wrapper for CFITSIOCFITSIO by Vivek Haridas (JHU)
Access to FITS tables and images from C#XML Web Services return FITS in attachment
Scientific PlottingUsing TeeChart LiteFast plotting of online data
SC4DEVO-1 Tamás Budavári (JHU) 11
Available Web Services
SDSS Web ServicesField Finder and SIAPSDSS Image CutoutSpectrum and Filter ServicesScientific Catalog ArchiveDensityMap Services
Other Relevant ServicesNED Services WrapperCosmic Distances
SC4DEVO-1 Tamás Budavári (JHU) 12
SDSS Fields and SIA
Field ImagesSearch for fields (HTM)Get all info, e.g. WCSReturns links to FITS
Simple Image Access
Wrapper on top of FieldsReturns links in VOTable
SC4DEVO-1 Tamás Budavári (JHU) 13
SDSS Image Cutout
Build JPEG mosaicsFor given (RA, Dec)Arbitrary zoom levelsOverplot catalog dataOverplot geometryMapQuest like navigationList of objects
Proper WSJPEG returned in DIMEor byte array
SC4DEVO-1 Tamás Budavári (JHU) 14
Spectrum Services
Public repository500,000 spectra (2B row)
Spatial search and more
Register & submit yours
Web siteOn-the-fly plotting
Building composites
Web servicesMore options and tools
SC4DEVO-1 Tamás Budavári (JHU) 15
SDSS Catalog Services
CasJobsAccess to a 1TB of data80M unique galaxiesQueue system for SQLMyDB
• 500MB remote DB• Upload and extract
Web servicesWeb site interfaceCommand-line client
SC4DEVO-1 Tamás Budavári (JHU) 16
SDSS DensityMap Services
A SQL query to image converterSelect x,y,f and build color coded f(x,y) image
SC4DEVO-1 Tamás Budavári (JHU) 17
Other Services
Wrapper for NEDName resolver functionSearch by coordinate
Available from
Cosmic DistancesVarious distance measuresUsing ΛCDM cosmology
NED ned = new NED();ObjInfo o = ned.ObjByName(“m101”);/* Use o.ra, o.dec, etc… */
Distance d = new Distance();float z=0.1, h=0.7, m=0.3, l=0.7;float r = d.Luminosity(z,h,m,l);
http://www.voservices.org
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