SkyServer: GLossary
DR7 Help
 Site News
 Cooking with Sloan
 Search Form Guide
 SQL Tutorial
 SQL in SkyServer
 Sample SQL Queries
 Query Limits
 Searching Advice
 Archive Intro
 Table Descriptions
 Schema Browser
 Web Browsers
 Data Publications
 SkyServer Sites
 Contact Help Desk

primary standardOne of the 158 stars on the SDSS photometric system that is observed by the PT to measure the extinction of a given night, and which is used to calibrate the magnitudes of the secondary standards (qv). The primary standard system is described in the Smith et al. 2002 AJ paper.