Star catalogs were developed by Marek Biskup (original DB structure, WWW interfaces) and Marcin Sokolowski ( DB development, optimization and data loading program )
                   
                  
The star catalogs in the "Pi of the Sky" experiment are based on PostgreSQL database. The database is used to store the reduced data after photometry and astrometry. It stores lightcurves of all objects observed by Pi cameras. The structure of the database is simple and consists of the tables Stars, Measurements, SuperStar and Frame. The database table Stars stores objects observed by one camera. Because same astrophysical object may be observed by multiple cameras, there is another table, SuperStar, which stores only single instances of astrophysical objects. Table Measurements stores all star measurements. Each row in the table Frame describes a picture taken by a camera. Relations between these tables are shown on the figure below :


Relations between SuperStar, Stars, Measurements and Frame


The database is optimized for fast searching. The fields often used in query conditions are indexed. The table Measurements is clustered, which means that all measurements of a star are located in
the same physical place on the disk. This provides fast access to star's measurements.
The cataloging procedure is being executed on-line, during collection of sky images. After cataloging finishes, optimization is being performed. Then the star catalog is ready for running off-line analysis scripts. The  prototype system  uses two databases for star catalogs:
The general statistics of existing databases is shown in table below :

Database name
 Period
 Number of stars
Number of measurements
 Typical number of measurements loaded per night
2004_2005
 20040701-20050801
 4.528.556
 791.301.754
aver20_2006 ( mirror )
 since 20061227
 2.798.142
 73.104.147
 1.300.000
scan ( mirror )
 since 20060523
8.258.607
 293.094.652


This databases are created on the remote computers in LCO and only most interesting data is synchronized to databases mirror on Warsaw computers. Example lists of interesting objects which measurements are synchronized every night is shown in table below :

Source of interesting objects list
 Type of objects
 Links to star catalogs ( aver20 and scan )
GTN
 blazars, polars, AGNs, variable stars
 aver20 / scan
WEBT
 blazars
 aver20 / scan
List of objects from Waldemar Ogloza
 variable stars ( binary systems )
 aver20 / scan


Analyzing scripts are launched on the remote computer and most interesting results are also synchronized to local computers.

mailMarcin Sokolowski 05.03.2007