Harvard Plate Collection Metcalf Telescope

DASCH
Digital Access to a Sky Century @ Harvard
A New Look at the Temporal Universe

Database Overview

The DASCH project data is currently organized in three MySQL databases: the scanner database, the photometry database, and the auxscanner database. The scanner database contains the logbook information and keeps track of the scanning and processing of plates. The photometry database stores the results of the photometry pipeline, which is implemented using tab-delimited ASCII Starbase Data Tables, and enables lightcurve plotting and statistical analysis of the photometry data. The auxscanner database contains miscellaneous secondary data derived from other tables and files to improve overall processing performance.

Scanner Database

The scanner database contains the following tables for management of the scanning process, support of the photometry pipeline, and support of this website.

globalContains global constants, control variables, and a time stamp.
locationsContains observatory latitudes, longitudes, and elevations.
ranges Associates plate series numbers with observatory locations and the expected time type (UT, EST, SAST,...) . Handles duplicate plate numbers.
series Contains a list all of the telescopes and their characteristics
classes Contains a lists all known plate classes
plates Contains a list of all known plates. Contains a record of low resolution photographs of the plates and the plate jackets. Contains an overall plate quality flag.
exposuresContains a list of all exposures and their characteristics as derived from the logbooks
catalog Contains transcriptions of the plate stacks card catalog. This data is being replaced by more detailed data from the logbooks themselves.
logbook Contains transcriptions of logbook data
lograngesContains the ranges of plate numbers in each logbook volume. This table is used in the verification of logbook transcriptions.
platerenameContains a table of renamed plates (deprecated)
scanPatternsContains a table of plate scan patterns executed by the digitizer.
scanLocations Contains a table of individual scan tile patterns for each scan pattern in the scanPatterns table
scans Contains a table of all plate scans executed by the digitizer
mosaics Contains a table of all mosaics generated from digitizer plate scans. This table contains World Coordinate Systems coefficients of each plate for the automated searches implemented by this website.
fithistory Contains a record of WCS fitting attempts (deprecated)
astromfithistory Contains the history of WCS fitting attempts after the transition to astrometry.net

Photometry Database

The database replaces a collection of tab-delimited ASCII Starbase Data Tables generated by the photometry pipeline. The intent of the photometry database is to provide rapid access to any lightcurve in the DASCH database. As currently designed, the photometry database contains the tables listed below. The primary spatial index into the database is a gsc_bin_index which divides the sky into 168,966,386 bins of height 1/64 degree in declination and approximately 1/64 degree in right ascension. This index is similar to the hierarchical triangle index developed for the SDSS, but optimized for rapid raster searches of the GSC2.3.2 star catalog. The illustration on the left shows how the tables are used to generate lightcurves.

photglobalContains global constants, control variables, and a time stamp.
photversionsContains version strings and identifiers in recognition of continuing development of the photometry pipeline. The versions are used to recognize and purge stale data from the other tables.
photseriesContains a copy of the series table index from the scanner database for more efficient MySQL queries
starsContains the star index based on either location or GSC2.3.2 reference ID and the GSC2.3.2 magnitude and color.
stars1Contains the star index based on either location or Kepler Input Catalog reference ID and the Kepler Input Catalog magnitude and color.
stars2Contains the star index based on either location or APASS Catalog reference ID and APASS magnitude and color.
photplatesContains a list of all plates processed by the photometry pipeline and global plate parameters, such as the plate scale, mosaic size, and Sextractor THRESHOLD level.
spatialbinContains derived parameters for the nine annular bins for each plate analyzed. These parameters include number of stars analyzed, limiting magnitude, upper limits, colorterm values, and bin rms.
localbinContains derived parameters for the 50x50 grid of local correction bins for each plate analyzed. These parameters include altitude in the sky; plate extinction; local calibration correction, number of stars, and correction rms value; and astrometry error measurements.
magnitudesContains values for each image on the plates. These values include GSC2.3.2 reference ID, plate coordinates, processing flags, magnitude, magnitude error, Heliocentric Julian date, and Sextractor shape parameters. This table is too large for efficient processing by MySQL and now consists of a series of binary files indexed by the gsc_bin_index.
starsummaryContains lightcurve statistics such as the number of points, DASCH magnitude and rms, clipped DASCH magnitude and rms, year range, and magnitude ranges. These statistics provide the basis for a search for interesting variable stars.
starsummary1Contains statistics of stars in the stars1 table processed with the Kepler Input Catalog instead of the GSC2.3.2 catalog
starsummary2Contains statistics of stars in the stars1 table processed with the APASS catalog instead of the GSC2.3.2 catalog
calibrationContains the relationship between SExtractor instrumental magnitude and GSC2.3.2 catalog magnitude for each plate and annular bin and the estimated RMS error for this relationship.
calibration1Contains the relationship between SExtractor instrumental magnitude and Kepler Input Catalog magnitude for each plate and annular bin and the estimated RMS error for this relationship.
calibration2Contains the relationship between SExtractor instrumental magnitude and APASS Catalog magnitude for each plate and annular bin and the estimated RMS error for this relationship.

Auxscanner Database

The auxscanner database contains tables which do not require periodic backup either because they are generated from text files or from other database tables.

loglinks Contains a linked list of all logbook page photographs for use by the logbook browser on this website.
logindexnew Contains the logbook volume and page number for all plates. Used by the logbook browser on this website.
coverage Contains a list of all plates indexed by one degree square regions of the sky. Used by the lightcurve generator.
disks Contains a list of all disks and raid arrays used by the DASCH project.
variables Contains the list of database variables listed in the Database Variables table below. Used for generation of VOTables

Database Variables

The remainder of this page contains reference tables useful mostly to the DASCH pipeline developers and to researchers who have been provided with DASCH photometry results.


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