Two Soviet cosmonauts who have been aboard the Mir space station for six months took a walk in space Thursday to repair a telescope, Radio Moscow said. The broadcast said Vladimir Titov and Musa Manarov were outside the station for five hours and 10 minutes and replaced a detector unit on an X-ray telescope. The telescope is on the Kvant orbiting observatory, which is attached to the Mir. The cosmonauts left the Mir station at 9:33 a.m., the official Tass news agency said. It said they had some problems unfastening the clasp holding the detector unit to the telescope.