29 Nov. 2019

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1st of fortnightly meetings

Attendees - Nic Erasmus, James O'Connor, Egan Loubser, Ali Ranjbar, Chris Mottram, Stuart Bates


  • We now have a Zemax file from Iain, this model makes the instrument a little more compact, (model sent to James).
  • Iain has requested the filters in the filter slides be increased to 35mm clear aperture (from their current 30mm)
    • From James, this increase would require either longer translation stages to position each filter slide or a reduction in the number of filters from 3x4 (5 position filter slides with one clear position in each), to 3x3.
    • Ali is looking to reduce the length of the grism assembly further (currently 40mm)
  • Ali has suggested a stepper motor be used to rotate the grism assembly to optimise for red and blue, looking into feasibility
  • James has requested LJMU start looking at their requirements for the instrument interface
  • We will be using compressed air for slit, calibration mirror and grism assembly deployment


  • James will speak with electronic control people at his end regarding controlling filter slides, stepper motor and solenoids
  • Chris Mottram looking at options to control stepper and filter slides
  • SAAO mentioned dissapointing results using Ardunio's in the past
  • Nic and Chris discussing software layers, which controls what
  • We should create a diagram showing all control and power items, and their relationships with each other


  • Iain raised concerns regarding substrate materials if we are to use use this instrument to observe further blue than 400nm


  • It was agreed we need to put a schedule together to co-ordinate effort appropriately

Action Items/ Decisions Req'd

  • Increasing the filter clear aperture - is this a no-go from a science perspective (reducing filters or longer filter actuators)? - Science team
  • Reduce length of Grsim assembly further - Ali
  • Purchase and test stepper motor - LJMU
  • Produce model of required instrument interface - LJMU
  • Decide how will actuators be controlled - Chris/Nic
  • Create diagram showing all power, control and motion requirements and relationships - LJMU
  • Create initial schedule - LJMU

Date of next meeting - Friday 13/12/2019