AO8T - USB or Ethernet?

Discussion in 'Guiding and Adaptive Optics - StarChaser and AO' started by Nigel Mayes, Feb 15, 2016.

  1. Nigel Mayes

    Nigel Mayes Cyanogen Customer

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    We have an AO8T setup with a STT8300M and FW8G-STT. The unit is controlled by The Sky and sits on a Paramount GT1100s.

    I have noticed that the guiding photos download much slower when the camera is connected via Ethernet cable instead of USB. Does this affect the efficiency of the AO unit, or just the frequency of the guide corrections?

    Thanks for any support you can offer.

    Cheers,

    Nigel
     
    Last edited: Feb 15, 2016
  2. Doug

    Doug Staff Member

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    Ethernet 100baseT is in fact slower than USB 2.0. You may get faster rates with USB.
     
  3. Nigel Mayes

    Nigel Mayes Cyanogen Customer

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    Thanks for your reply. I realize the data transfer to the computer is slower over ethernet, but does this affect the 10Hz adjustments that the AO unit makes. Is it closed loop, or does it rely on feedback from the computer for each guide image that is made? If the computer is involved, then there would definitely be an advantage to using the USB connection.
     
  4. Doug

    Doug Staff Member

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    The computer is involved in the loop, so the interface does matter.

    The best way to speed up the guide rate is to use a smaller tracking box so there is less data transferred to the computer. But using the faster interface will help.
     
  5. Nigel Mayes

    Nigel Mayes Cyanogen Customer

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    Thanks, Doug.

    I am guessing that shorter exposures with the guiding CCD will also improve the performance of the AO unit as well?
     
  6. Doug

    Doug Staff Member

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    Yes, the guiding rate is fundamentally limited by the guider exposure time. If you take exposures over 0.1 second you can't guide 10X a second. So you want to use the shortest exposure time that gives you good signal-to-noise ratio.
     
    Nigel Mayes likes this.

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