General AOX usage question

Discussion in 'Guiding and Adaptive Optics - StarChaser and AO' started by Dave, May 20, 2020.

  1. Dave

    Dave Standard User

    Joined:
    Nov 20, 2014
    Messages:
    106
    Hi folks,
    I am not having any operational issues with my AOX. I just had a general question regarding its usefulness in my particular situation and there is a lot of confusion out there regarding what the AO is supposed to do or not do.
    So in the last couple of years of my own personal experience with it I have come to these sort of general conclusions:
    1) When the seeing is great, the AOX does improve the fwhm results on my subframes. When the seeing is average it doesn't seem to help and when the seeing is below average it makes the results worse in that the stars can be round but they are bloated. Most of the time my local seeing is only average so I am not experiencing any significant benefit from the AOX
    2) The best results appear to happen when exposure times are extremely short such as 0.05 to 0.1. This results in the highest frequencies of oscillation I can attain e.g 6hz or so. The downside to this is that you have to use a very bright guide star like 6 magnitude or so

    Some people using AO technology are saying it helps with wind deflections and improves guiding if you are having trouble without it. I believe these claims are misguided (no pun intended) and my own conclusion is that in average seeing ,the AOX benefits are marginal. If you think I should be getting better results over a wider range of seeing conditions let me know and I will re-examine.

    Thanks
    Dave
     
  2. Colin Haig

    Colin Haig Staff Member

    Joined:
    Oct 27, 2014
    Messages:
    3,751
    Dave, many users report improved guiding performance, tighter stars (eg smaller PSF), and improvements when seeing is "slow". eg upper winds are not rapid; stars are not twinkling a lot.
    Faster guide star exposures are necessary, as you want several corrections per second. 6Hz is ok; 10Hz is attainable on some systems.
    I'm not sure what you mean by "below average" or "average" seeing. It varies widely based on local geography, elevation, weather including upper winds, and of course the optical system you have.
    My local version of "average seeing" is usually about 2+ arcseconds; sometimes worse. As they say, "your mileage may vary".
    We have a few customers with large (17-24 inch) scopes and the AO-X results are superb. We also have a few with crappy mounts, and they get much better results with AO on.
     
  3. Dave

    Dave Standard User

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    Nov 20, 2014
    Messages:
    106
    Thanks Colin. My average seeing is 2-2.5. Sometimes worse. Only very occasionally better. I have a 16" scope on a Paramount MEII (with the on axis encoders). FL 2800mm. I guess I am trying to get a sense of what should my expectations be for these conditions. It does seem to help when the seeing is better than average (2 arc sec or less) but otherwise not. Does this make sense?
    Dave
     

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