Miscellaneous links	Notes
Astrometry	.
ICRF / ICRS	International Celestial Reference Frame / System
IAU WG Reference Frames / densification	Progress on optical catalogs
Radio - optical reference frame link	.
Hipparcos Space Astrometry Mission	Optical ICRF
Tycho-2	2.5 million brightest stars on the ICRS
GSC-II	1 billion objects from All-Sky Schmidt plates
PMM	Precision Measuring Machine projects, Flagstaff; USNO catalogs from Schmidt plate scans
USNO-A2.0, USNO-B1.0	1 billion objects from All-Sky Schmidt plates
SuperCOSMOS	Catalogs from Schmidt plate scans
trigonometric parallaxes	Yale, 4th edition, 1995
AC2000	early epoch positions, around 1900, for 4 million stars
UCAC	U.S.Naval Observatory CCD Astrograph Catalog - high precision astrometry to 16th magnitude
SPM2	Southern Proper Motions, -25 to -40 degrees declination, not complete, 2 epoch data with link to galaxies
Redshift Catalogs	.
CfA Redshift Catalog	The famous 'original' redshift survey
IRAS PSCz Catalog	IRAS Point Source Redshift Catalog
ENACs	ESO Nearby Abell Cluster survey
Miscellaneous	.
Wide-Field Plate Database	.
astrophysical CATalogs support System (SAO, Russia)	.