Quote:
Originally Posted by Shiraz
Not convinced that it is going to make a huge difference Paul. There is a comprehensive literature that shows that seeing correction is only possible using AO over a small region surrounding the guide star. There is a bit of marketing hyperbole out there suggesting that AO systems can "correct for seeing", without saying under what conditions. The physics shows how limited that correction really is. AO is likely to be very useful for cleaning up wind and mount jitter/tracking effects, particularly if you take long subs. But as far as I can tell, it cannot correct for seeing over wide fields (eg > 1 arcmin) - it would be great if it were otherwise and I would be very pleased if someone could demonstrate why the limitations identified in the theory apply to professional systems, but not to ours.
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I have been using SBIG Adaptive optics for some time and I can see value in them.
That said, I was recently at the Hale Palomar 200 inch observatory with their head engineer, and the techs were installing the adaptive optics unit at cassegrain focus. (AO is only at cassegrain not prime).
The adaptive optics they use has 1000 actuators deforming a mirror at 1000 cycles per second. And all the cables between the computers to the adaptive optics unit are hand made, they are called dreadlocks, because they sure look like it. To get the computing power to cause 1000 actuators to correct 1000 times per second is extraordinary. Thinks about this, it reads a sensor makes 1000 calculations to where best 'atmospheric correction' for each actuator, sends that signal for the actuator, after it moves, checks the result recalculates and repeat.... 1000 times per second. There is huge amount of processing power needed to to do this and to get that power, There are racks and racks of computers hanging below prime focus that RUN AO corrections ONLY, no other functions. Because these computers generate a lot of heat, (and heat released into the air is a bad thing for seeing around the telescope) the 200 inch drags glycol coolant pipes around the floor to external coolers to shed the computer generated heat.
Amateurs are using a single corrective prism in 2 axes in an ao unit at around 1 to 10 hertz, that uses a fraction of your desktop computers processing power. So it not at all comparable to professional systems.
So in reality, the amateur AO is not in the same league, So Is it worth it?
I think so. Here's why:
To make an auto guiding correction with a mount requires a movement of mass of all half your mount and all of your optics and imaging train. Then there is cables that may resist movement and you have over effects like oscillations, backlash etc.
Or you could move a small prism weighing a few grams at 10 times the speed....
Do I think amateur AO correct for seeing? Don't know. But it makes one hell of a fast auto guider and better stellar profiles. That will do for me.
I am just setting up a system with AO and the new Large format ONAG. I am very keen to see how this works, because infrared is less affected by seeing than the visual spectrum. So Ray according to your reading, As the onag guides from the centre of the cameras field of view, not off axis, it is more likely to do correct for seeing. What do you think?
Brett