Some fields, such as astrometry, are purely astronomy rather than also astrophysics. The degradation is more severe for the RVS spectrograph than for the astrometry measurements. Based upon parallax measurements with the Hipparcos astrometry satellite, Kapteyn's Star is from the Earth. Based upon parallax measurements made with the Hipparcos astrometry satellite, Hamal is about from Earth. Radar astrometry in January 2005 further refined its orbit solution. The telescope can also be used for highly precise astrometry. It relies on the mathematical methods of spherical geometry and the measurements of astrometry. The precise measurement of stellar positions is part of the discipline of astrometry. A fundamental aspect of astrometry is error correction. As determined by the Hipparcos astrometry satellite, it is approximately from the Sun. No. 61 in Perth on "New Problems of Astrometry". In 2009, the discovery of VB 10b by astrometry was announced.