WFI Overheads

The following is the list of overheads for the WFI:

The WFI Overheads
Pointing the Telescope  Over large angles, ~3000 arcsec/sec
Typical pointing time between 30 seconds and 2 minutes
Changing Filter  45 seconds + 2.5 seconds * difference in position number of the filters
e.g. Changing from filter position #4 to filter position #12
45s + 2.5*(12-4) = 65 seconds
Software Overheads 
  • No preset, no change of filter = 5 seconds
  • Preset to same field (i.e. telescope doesn't actually move), no change of filter = 25 seconds
  • Aquiring a Guidestar **  <1 minute
    Detector Readout  27 seconds
    File transfer to instrument control workstation and RTD  45 seconds (i.e. 27 seconds for readout + 18 seconds)
    Focussing  ≤10 minutes
    Move to Gap Template  2 * [Exposure time + 45 seconds (readout and transfer) + ~1 minute (find star and set coordinates)]
    At least! (depends on how accurate you want the positioning)

    **NOTE: If you have COMBINED OFFSET = F (i.e. if you have large offsets between each image), this overhead applied for each image within your dither sequence.

     
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