European Southern Observatory New Technology Telescope

General :
Observations :
Operations :

Grating Focussing

To focus a grating (blue , red or echelle) :

• Foreword:
  • REMD_all_tec_SetFoc and BLMD_spec_tec_SetFoc recompute the parMode parameter ( focus encoder position at 0 degrees Celsius ) in the focus formulae for REMD/focr and BLMD/focb respectively, and modify it upon confirmation by operator.
    This formula tuning is always performed at the same wavelengths : 700 nm in red , 400 nm in blue.
    
  • REMD_all_tec_CheckFoc and BLMD_spec_tec_CheckFoc replace REMDST04 REMDST05 and BLMDST04
    
  • REMD_all_tec_CheckFoc allows to compute the focus for the wavelength ( grating ) or cross disperser (echelle) requested by the observer: it then presets the initial value in the focus (Echelle) or focus offset (Grating) dialog box for other REMD templates.
  • BLMD_spec_tec_CheckFoc allows to compute the focus at the wavelength requested by the observer: it doesn't preset any corrective value as the BLMD formula is accurate enough to make unnecessary a correction by the template.
    
  • All these template OBs may be found in $INTROOT/SYSTEM/COMMON/TEMPLATES/OBD.
• Procedure:
  • First run REMD_all_tec_SetFoc or BLMD_spec_tec_SetFoc to minimize REMD or BLMD focus error
    Only accept the proposed correction if it looks reasonable ( more then 10 e.u. :if more than 50, verify and report ).
    
  • Then execute REMD_all_tec_CheckFoc or BLMD_spec_tec_CheckFoc to verify that focus error is lower
    than at most 2 degrees Celsius or to set the wavelegtn correction value for REMD _obs_ and _cal_ popup windows.
    

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