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Torben Anderssen. Profile picture.

Torben Andersen

Professor emeritus (Leave of Absence)

Torben Anderssen. Profile picture.

From Euro50 towards a European ELT


  • Arne Ardeberg
  • Torben Andersen
  • Jacques Beckers
  • Michael Browne
  • Anita Enmark
  • Per Knutsson
  • Mette Owner-Petersen

Summary, in English

With Euro50 as a convenient telescope laboratory, the Euro50 team has continued development aiming at a European extremely large telescope (ELT). Here, we give a progress report. The needs of science and instrumentation are briefly discussed as is the importance of photometric stability and precision. Results are reported from work on integrated modelling. Details are given concerning point-spread functions (PSFs) obtained with and without adaptive optics (AO). Our results are rather encouraging concerning AO photometry and compensation of edge sensor noise as well as regarding seeing-limited ELT operation. The current status of our development of large deformable mirrors is shown. Low-cost actuators and deflection sensors have been developed as have hierarchic control algorithms. Fabrication of large thin mirror blanks as well as polishing and handling of thin mirrors has been studied experimentally. Regarding adaptive optics, we discuss differential refraction and the limitations imposed by dispersive optical path differences (OPDs) and dispersive anisoplanatism. We report on progress in laser guide star (LGS) performance and a real-time online experiment in multi-conjugate AO (MCAO). We discuss ELTs, high-resolution spectroscopy and pupil slicing with and without use of AO. Finally, we present some recent studies of ELT enclosure options.


  • Lund Observatory - Has been reorganised

Publishing year







Proceedings of SPIE - The International Society for Optical Engineering


6267 II

Document type

Conference paper


International Society for Optical Engineering


  • Astronomy, Astrophysics and Cosmology


  • Hierarchic control
  • Laser guide star (LGS)
  • Optical path differences (OPD)
  • Differential refraction
  • Point spread function (PSF)
  • Extremely large telescope (ELT)
  • Edge sensors

Conference name

Ground-based and Airborne Telescopes

Conference date

2006-05-24 - 2006-05-31

Conference place

Orlando, FL, United States




  • ISSN: 1996-756X
  • ISSN: 0277-786X