Is Adaptive Optics worth it?

[Daveskywill]

Hello:

I thought with those professionals (telescopes) version of adaptive optics

what they do is somehow aim a laser into the air in the direction of the sky they're wanting to image.

And then based on the image of it they see reflected by picking it up in a side scope, the imaging program knows (somehow) through programming how to make the changes in the image picked up by the main optics.

It's really interesting. With the first case, the change to the final (main) image is done through the computer. But then there's seems to be a version where the main image is manipulated by having actuators on the back of a reflective mirror. And these are manipulated in real time while the image is taken to counter act for bad seeing and for mistracking.

The version of AO that SBIG and Orion is selling doesn't use a laser to shine. But I believe use that actuator idea.

Can anyone here tell me if (if money wasn't a problem) would AO by one of these suppliers be worth it.

Like they say it does better than Autoguiding alone. And it takes care of seeing problems as well as tracking problems. So it a pretty attractive idea.

And PS: is SBIG's AO compatible with any of the SBIG camera's, or specifically the ST-2000? And with respect to that earlier post someone did on CCD's, how does "ghosting" and QE have to do this these cameras?

I know for example if you want to see the type of chip (for SBIG) cameras, it's on their website beside the name on their price page.

Thank you.
David

[DavidTrap]

It was described by one of the presenters at AAIC as "super guiding", IIRC.

Personally, I think it's a bit of a stretch to call it "adaptive optics", especially if it causes someone to consider it in the same league as what is done by professional observatories.

I'm not trying to argue it doesn't improve image quality.

DT

[RickS]

Starlight Xpress call their version "active" optics, presumably to differentiate it from the more sophisticated (and expensive) adaptive optics. I have one of their units on order after hearing good reports...

Cheers,
Rick.

[gregbradley]

I haven't used one. But I have read many times that the gain from an AO unit SBIG or otherwise is on long focal length scopes.

How long?

Arbitrarily - longer than about 1260 to 1500mm.

If you look over the net you generally would not find one used under about 1500mm focal length.

The reasoning would be at >1500mm the seeing starts to become quite noticeable on the guide star and images.

Greg.

[bert]

I use mine for 918mm fl and I wouldnt be without it.

I have 2 different sbig adaptive optics units. I have an a08 and a aol.
The ao8 is used on a cheap mount and I get pinpoint performance from a cheap mount and Im really happy with its performance. The aol is mounted on a 12.5rc, 2100 fl with a moag. This system is still in the commissioning stage.

David was quoting Greg Terrance from fli when he said it was a super guider. It was a dissmissive comment, as fli did not think it was worth developing, and I have reason to believe fli's position on ao maybe changing.

Think of ao this way;

If you can get a good guide star, you can really chase the seeing with hi speed guiding and have up 30 corrections per second. Sweet.

If you cannot get a bright guide star and have to use a slow correction (say over a second) you are still better off with ao. Why?

Conventional guiding means throwing around the mass of your mount, telescope, camera et al to try and correct for errors. When using the ao even at the same guide rate, you are only moving a few grams of an optic to make the same corrections, and bypassing the oscillations, gear issues etc involved with conventional guiding.

Is AO worth it? I think so.

Brett

[Bassnut]

Id agree with Brett generally, when it flys, its a killer, but it has "issues".

To get a bright enough guide star for 30hz corrections is very rare indeed (close to the object imaged). You have to be sure before purchase that you have enough back focus to handle all the gear required plus adaptor hell (about 8 inches). Forget internal guide AO on an SBIG youll need an AOGer and external guide cam etc.

I look at it this way. If you want to bang out a variety of objects in a reasonable time, you wont use it much, or the AO advantage if you do wont be huge . If you want to produce a standout masterpeice, with all the time and patience that involves, on a rare object that has a mag 3 guide star in exactly the right place, AO is the last mile, essential.

[Alchemy]

My take on it is this......

Consider a car, you can put racing tyres on it, but without the suspension, steering, motor, etc etc you won't get the real value from it.

So if you are using an average mount , an average scope, an average camera ( pixel size etc) the potential benefit will not be realized.

To gain the benefit you will need a mount with backlash etc that can cope with multiple updates per sec, a camera with fine enough resolution that a difference can be seen, plus good optics, and of course a FL long enough to notice the turbulence in the atmosphere.

But you won't take any worse pictures with it than without.

[bert]

The moag/aol chews some backfocus alright!

Luckily for me the ao8 is on a colour cam so I can use the internal guider....No filters, no aog. So theres room for the df2 and pyxis rotator, Im still thinking of cutting the tube so I can slip in a reducer!

Brett

[Terry B]

I have an AO7 permanently on my camera. It certainly used up back focus so that I can't use the focal reducer on my VC200l and EQ6. This means I image at 1800mm. Using just my guide scope I get a bit of flexure that becomes apparent with 5min exposures. I can use the AO7 and keep an object on exactly the same pixels. When I use it is for time series photometry. It corrects the guiding much better than the guidescope. This reduces error in the data. It can't always be used but I can usually get a guidestar with 1/4-1 sec exposures.

[bert]

Terry,

Anacortes has the ao8 on sale for $495us, and can be used with a vc200l with the reducer and an sbig st camera. I have a vc200 and have done it, it was annoying for me because I had to swap out my df2 focuser for a robofocus. I cant remember if I had the rotator in at the same time.

Brett

[Terry B]

Thanks Brett. I'll look into it.