RESUMO
A system is described to control the figure of a large telescope primary mirror that is composed of many individual segments. The geometry considered, employing hexagonal mirrors, allows a simple and economical control system. The system is shown to be reliable and effective in continuously maintaining the figure to the precision required for optical astronomy.
RESUMO
A mirror has been fabricated with the shape of an off-axis section of a paraboloid by grinding and polishing a sphere into a prestressed blank. The applied stresses were then removed allowing the mirror to spring into the desired paraboloidal shape. The 36-cm diam off-axis section deviated 9.9-microm rms from the polished sphere. The final surface deviated 0.03-microm rms from the desired off-axis section.
RESUMO
The age of a sample of carbon dioxide has been determined by accelerating the carbon with a cyclotron and detecting the carbon-14 ions in the beam. Nitrogen-14 was eliminated as a background through the use of a range-separation technique. To avoid all possibility of experimenter bias, the measurement was conducted in a blind fashion.
