2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/1599The quest for the distance of the Vela and Geminga pulsars yielded, so far, a set of four WFPC2 images for each object. The availability of couples of images taken at the same period of the year, thus affected by the same parallactic displacement, prompted us to use Vela and Geminga as test cases to assess the reliability of HST astrometry.4 pages, 2 PostScript figures, uses psfig.sty. To appear in the proceedings of A Decade of HST Science (Baltimore, USA, April 2000)Astrophysicstext