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

great circle coordinatesOne of the two main coordinate systems utilized by the SDSS. In this system, mu and nu are spherical coordinates (corresponding to ra and dec) in a system whose equator is along the center of the stripe in question. The stripes of the survey are great circles which all cross at (RA, Dec) = (95, 0). The stripes are defined by their inclination with respect to the equator, and are indexed by integers n such that the inclination of a stripe is -25 + 2.5n. Thus, stripe n=10 corresponds to the Equator. Astrotools provides utilities to convert to and from these, such as GSCToSurvey. The design is that the area covered by the imaging on a given stripe (the so-called OK_SCANLINE area in the north) is a 2.5 degree wide rectangle centered on nu=0 in Great Circle coordinates.