Quote:
Originally Posted by alpal
Hi Paul,
Let me chime in with what I know:
I would suggest you try it out if at all possible.
I have over 20 years experience with industrial closed loop control systems -
which is exactly what a telescope mount with an OAG is -
in fact - it's a dual axis closed loop control system RA & DEC.
I have found that all the best industrial systems use what is
known as a nested loop:
this means that there is one closed loop operating at one frequency -
let's say 1 Hz and another one nested inside it operating at say 10 Hz.
The ratio is normally 10 to 1.
This gives much greater accuracy than a single closed loop axis.
Notice that the normal ratio is 10 to 1.
That is important otherwise the 2 loops fight against each other & produce poor results.
Therefore - if your OAG system is operating at 1 Hz & your AO is at 2 Hz there would not be an advantage.
You would need a bright guide star to get 10 Hz for Adaptive Optics.
cheers
Allan
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Interestingly this is exactly what I do. I have 2 scopes side by side on the same mount. One has a spectrograph on it and I will guide on the slit using a STi at 1 or 2 sec exposures. This is fine for the spectrograph. Sometimes I will simultaneously image through the second scope for photometry. If the target is dim requiring long exposures I will use the AO unit to guide the photometry image usually with 0.2 -0.5 sec exposures depending on the filter. There is a bit of differential flexure between the 2 scopes and the AO corrects this very well. It would never have enough flexure to exceed the range of the AO unit.