Context :

Aims : We measure absolute trigonometric parallaxes and proper motions with respect to many background galaxies for a sample of ten ultracool subdwarfs .

Methods : Observations were taken in the H -band with the OMEGA2000 camera at the 3.5m-telescope on Calar Alto , Spain during a time period of 3.5 years .
For the first time , the reduction of the astrometric measurements was carried out directly with respect to background galaxies .
We obtained absolute parallaxes with mean errors ranging between 1 and 3 mas .

Results : With six completely new parallaxes we more than doubled the number of benchmark ultracool ( > sdM7 ) subdwarfs .
Six stars in the M _ { K _ { s } } vs . J - K _ { s } diagram fit perfectly to model subdwarf sequences from M7 to L4 with [ M / H ] between - 1.0 and - 1.5 , whereas 4 are consistent with a moderately low metallicity ( [ M / H ] = -0.5 ) from M7 to T6 .
All but one of our objects have large tangential velocities between 200 and 320 km/s typical of the Galactic halo population .

Our results are in good agreement with recent independent measurements for three of our targets and confirm the previously measured parallax and absolute magnitude M _ { K _ { s } } of the nearest and coolest ( T-type ) subdwarf 2MASS 0937+29 with higher accuracy .

For all targets , we also obtained infrared J,H,K _ { s } photometry at a level of a few milli-magnitudes relative to 2MASS standards .

Conclusions :