We have conducted a search for new stars of high proper motion ( \geq 0.4 arcsec yr ^ { -1 } ) using POSS II fields for which an extra IIIaF ( red ) plate of good quality exists , along with useable IIIaJ ( blue ) and IV-N ( infrared ) plates taken at epochs differing by a minimum of 1.5 years .
Thirty-five fields at Galactic latitudes |b| \geq 20 ^ { o } were measured , covering some 1378 deg ^ { 2 } , or 3.3 % of the sky .
Searches with three plate combinations as well as all four plates were also made .
Seven new stars were found with \mu \geq 0.5 arcsec yr ^ { -1 } , which were therefore missed in the Luyten Half Second ( LHS ) Catalog .
One of these is a common proper motion binary consisting of two subdwarf M stars ; another is a cool white dwarf with probable halo kinematics .
As a test of our completeness – and of our ability to test that of Luyten – 216 of 230 catalogued high proper motion stars were recovered by the software , or 94 % .
Reasons for incompleteness of the LHS are discussed , such as the simple fact that POSS II plates have deeper limiting magnitudes and greater overlap than did POSS I .
Nonetheless , our results suggest that the LHS is closer to 90 % complete than recent estimates in the literature ( e.g 60 % ) , and we propose a reason to account for one such lower estimate .
The conclusion that the LHS Catalog is more complete has implications for the nature of the halo dark matter .
In particular it strengthens the constraint on the local density of halo stars , especially white dwarfs at M _ { V } \sim 17-18 .