Simple: For example, one can simply, instead of imaging for 5 minutes, make a stack of 30 second exposures. Then the effect of the seeing that creates these halos is also smaller.
But in the picture above, the author must have had simply good seeing. And he has an "NEQ6 Pro II Tuning Belts + EQMOD".
So yes, if you have a good mount, and good seeing conditions, then you can make good images without ao.
Additionally, the picture with the ao was made by a meade sc. The picture of your example is an apo.
An apo usually has much sharper stars. This is because it has no secondary. And the quality of certain sc's from a manufacturer named M.... is known to be problematic. When the optics itself is not very sharp, the diffusion of seeing becomes worse. Assume you have a star centered at one point. If it is for a milisecond somewhere else, it generates a smear. However, if the telescope is good, and it shows the center brightly, the smear is not that important and "scaled away" by your image viewing program. On the other hand, if the telescope is bad, the center won't become very bright in comparison with the smear so you get more annoying halos.
Moral of the story: Use an APO for astrophotography that does not have a secondary in its lightpath.
Why is that "counterproductive"? The system that sends commands to the mount is just phd guiding, which can operate the ao.
phd guiding can send the guide pulse to the mount directly or via ao to the mount. It makes no difference.
Also, there is nothing lost if phd guiding detects that the star is out of the ao correction range and sends a mount bump to pull it back into the frame.
Please note that the sx ao is just a moving glass. For phd guiding, the sxao is just an additional correction interface that takes preference over sending pulses to the mount. Nothing else
The problem, that is, the thing which makes things slower with the sx ao are the following:
a) the download of the guiding image from the camera takes long and
b) that you do not have guidestars avaliable in your off axis guider which you can see at 0.01 seconds or better.
Additionally, i think they have changed something in phd guiding that it is not using the cameras in videomode, which makes things additionally slower.
I must test if I can get the performance from early days back when I perhaps use windows video drivers...
But the problem is certainly not that the ao can also command the mount. It is also not the ao itself.
The sx ao has a reaction speed of 5ms. The problem is the slow speeds of video download in phd guiding, the download time of the guide camera and the guide camera's sensitivity.
But many of these things can be corrected with a software that is tweaked for faster speeds and with a faster guiding camera.
For example, using roi speeds things up in phd guiding. But, as I said, I noted a slowdown in phd guiding recently, that is on their end.
