The SPM4 is the most extensive SPM catalog version to date and
in many ways is the culmination of the 47-year Southern Proper Motion
program. Absolute proper
motions, positions, and B,V
are given for over 100 million stars and galaxies, down to a magnitude
of V=17.5. Sky coverage
is from declination -20
degrees to the south celestial pole. Cross
references to the 2MASS near-infrared catalog are also included, as is
2MASS JHK photometry.
The catalog is based on a combination of photographic and CCD
observations, all made with the 51-cm double astrograph of
Observatory in El Leoncito, Argentina. The
photographic plates were scanned using the Precision
Measuring Machine at the US Naval Observatory's Flagstaff Station. The
raw pixel data were saved and later analyzed at the US Naval
Observatory in Washington to obtain image centers and photometric
indices for all detectable images. CCD observations comprise the
second-epoch astrometry for roughly two thirds of the area
covered. The absolute proper motions are tied to the ICRS at the
bright end, via Hipparcos stars, and to external galaxies at the faint
end. The final precision of the SPM positions and absolute proper
motions is approximately 30 to 150 mas and 2 to 10 mas/yr,
respectively. Systematic errors in the proper motions are still
being evaluated but are estimated to be on the order of 1 mas/yr.
The SPM4 Catalog is available
for ftp download as a set of
bzip2 and plain ascii files, including an explanatory readme file and
simple Fortran code for extracting subsets of the data. The total
size of these files is approximately 4.3 gigabytes.
To obtain the SPM4 Catalog via ftp, click here.
Return to the Astrometry Home Page
This page last modified by T. Girard - November 19, 2019.