European Southern Observatory New Technology Telescope

General :
Observations :
Operations :

EMMI Filter Setup

This procedure is identical for red and blue filters. The EMMI function corresponding to the red (blue) filters is FILR (FILB). The filters used on EMMI are circular with a diameter of 85 mm. It is also possible to use circular filter of diameter 60 mm in which case a special cell has to be used. One has to keep in mind the effects:
- red arm: uniform flux loss in the field equivalent to stepping down the mirror size
- blue arm: variable flux loss in the field and vignetting.

• Press EMMI emergency stop button at the center of EMMI cover.
• Get the boxes containing the filters you want to mount from cupboard #1.
• Remove the large red (blue) cover from the front of EMMI.
• On the EMMI configuration panel, select filter pos and click move to load on FILR (FILB).
• Remove the filter in this position and mount the new one. If a filter is dusty
  clean it with some pressurized CO2.
• Be careful to mount filters with a red type cell (filter tilted by 5 or 10 deg with respect to the cell) in the red arm and filters with blue type cell (no tilt) in the blue arm. If this is not the case, warn the astronomer of possible problem:
  - astigmatism for a red filter on the blue arm
  - ghost image for a blue filter on the red arm
• Re-install the removed filter in the container and re-store it into cupboard #1.
• Put back EMMI cover into position.
• Release the emergency stop button.
• Declare new filters in EMMI configuration panel
• Click Backup under File submenu.

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