The Washington Double Star Catalog is a database of double stars
maintained by the USNO, that combines information from earlier
such catalogs.
It uses a Latin-alphabet code-abbreviation indicating the
discoverer, such as STF for Friedrich Struve rather than the
traditional Σ and in addition to the traditional designations,
such stars are often cited using these codes (e.g., STF2740;
for Σ2740; see Struve Catalogs) or with a WDS designation
(WDS 20568+6134 or WDS J20568+6134).
The WDS is an outgrowth of the IDS
(Index Catalog of Visual Double Stars),
developed and previously maintained by Lick Observatory.