Re: What's the effect of imaging through jet stream?


Cheng-Yang Tan
 

Hi Glenn,
  Good to know that my earlier problem was also observed by you. Unfortunately, l am not completely convinced because my setup is torn down and reinstalled each evening. Although I always set up close to the same spot on the sidewalk, and I try to be consistent setting up, I really cannot guarantee that each install, PA is identical.
   Everything went smoothly last night though despite the wind. Who knows what the real cause is if it’s not the jet stream the previous night.

On Sunday, May 31, 2020, 8:58 AM, Glenn <public@...> wrote:

cytan,

I generally have poor local seeing, but I am amazed at the variation that is possible. On good nights, guiding with my Mach1 (last generation) is around 0.3-0.4 arc seconds and the resulting HFD of the subframes is in the 2-3 range. On bad nights, particularly when the jet stream is a factor, guiding is 1.5 arc seconds or worse and the HFD is much higher. On the worst night in memory, my HFD was 10+! I thought there was something wrong with my optics—the stars looked like giant snowballs and refocusing did not improve them. But a couple of nights later, guiding and image quality had returned to normal. So in my experience the jet stream can significantly degrade both guiding and image quality. 

Regards,

Glenn

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