Solar Adaptive Optics

[cshahar]

I have been doing research on adaptive optics specifically for solar imaging. Adaptive optics are an indispensable tool for ground-based solar telescopes, enabling them to overcome adverse seeing conditions, so they can obtain diffraction limited views. In fact, they are credited with reviving ground-based solar astronomy since their inception. But these tools are more complicated to construct than the ones used for nighttime imaging, basically because of the difference between using stars (pinpoints) to measure how the light is distorted, versus large, low-contrast targets comprising an infinite number of point sources.

Unfortunately, there does not seem to be commercially available solar adaptive optics instruments yet. I was wondering if anyone has come across these types of instruments? It would seem less commercially viable since "serious" solar imagers / observers represent only a small percentage of those engaged in astronomical pursuits.

-Charles

[cshahar]

Found this website and am in contact with the manufacturer. They don't list the prices for their deformable mirrors, and I am afraid to ask. I am not even sure whether they apply to amateur instruments. Has anyone heard of them?

http://www.alpao.com/Applications/Adapt ... ronomy.htm

[eroel]

Charles:
During the 1990's, I was in touch with Dr. Donald G. Bruns of Stellar Products, I bought the AO-2 adaptive system for planets and moon, but just used it for a Mars opposition. I still have the system and I will try it on the sun. (I had forgotten that I have it)
Don´t know how good it would be on the sun, but it was meant for extended objects.
At that time, the cameras we used were terrible, so I don´t know if it still works with newer ones, so I will look for the manual to remember how to use it.
What I recall, is that when looking at Mars, you turned a small knob and the planet stopped jumping, a really impressive result on those days.
Ignore if Dr.Bruns is stil around, this was the first commercial adaptive optics system around.
Best regards,
Eric.

[cshahar]

Wow Eric. That sounds exciting. Please let me know how your tests turn out. From what I can see, AO is really a promising way to improve resolution and image quality, particularly with larger apertures. I am interested in any commercially available system that can do that.

-Charles

[eroel]

Charles, found the site.
http://www.stellarproducts.com/
Regards,
Eric.

[cshahar]

Thanks Eric. I found it too, and just sent him an email. He mentions the planets and the moon, so it will be interesting to know if the AO unit also works for solar imagery.

[GaborKiss]

Very interesting topic. 15 years back when I was 17 years old having my 10" Cassegrain, we could hear about Adaptive Optics. I was quite sure that they will be commercially available within 10 years. Unfortunately it did not happen and I don't see anyone going to this direction. Still the best planetary imagers are chasing the seeing conditions (Damian Peach just arrived to Barbados). The AO would make a perfect sense and would change to game of high-res imaging, but I am afraid we perhaps have to wait another 10-20 years or it won't be available at all in the future for amateurs.

Cheers,
Gabor

[cshahar]

I got the following cryptic reply from Don Bruns:

Sorry, all adaptive optics only work on targets a few arcsecond across. AO-5 is still in development.

I'll try to find out more...

-Charles

[cshahar]

Final word from Don:

Sorry, the AO-5 will not work on solar targets. No adaptive optics
concept I know of will work on the sun, except for fast image
stabilization, which is the equivalent of very short (1 millisecond)
exposures. Because of atmospheric isoplanitism, that only works on
targets up to 30 arcsec across.

[eroel]

Charles:
He also shot some lunar craters, so probably with a small sunspot it could work. i will try but the system is at my rural observatory and don´t know if this weekend I can make it there.
Nice that he still is working in the AO-5 system.
Regards,
Eric.

[cshahar]

Fantastic. Let me know Eric. In the meantime I will ask him about the craters.

[cshahar]

Here is the response from Iris AO:

My office manager told me that you were looking for information on solar Adaptive Optics Systems.
Our company is specialized in building segmented MEMS-based AO system. We fabricate segmented deformable mirrors and design AO system (including optics & software) for customers.

Could you let me know what type of AO system are you interested in designing?

About our products:
The PTT111-5 deformable mirror (DM) with its drive electronics is $~17,500 per unit. In this case the DM has a metallic coating (Silver, Aluminum or Gold), a stroke of 5 um and a control rate up to 4 kHz.
The estimated delivery time is 6-8 weeks ARO.
We offer volume discounts of 5% for Q=3-5, and 10% for Q=6-10.
We can also provide ultra-flat mirrors (<7 nm rms error) (+$5K) and mirrors with larger stroke (8 um) (+$7.5K) for astronomical or biological applications. We offer single-wavelength dielectric coatings (+$7.5K) for the DMs or for the wavelength and angle of incidence you specify. We also offer special packaging for harsh environments (+$5K). This packaging is particularly useful for high power lasers.

Finally, we can also provide a PCI-based (32-bit OS only), faster set of drive electronics (+$5K). This provides up to a few kHz without latency, with an optional externally Playback Modes, useful for scanning-based applications.
The PTT489-5 deformable and a control rate of up to 4 kHz. The estimated delivery time is 14-18 weeks ARO.

Cordially,

Franck M.



Franck Marchis, Ph.D.
Senior AO Application Scientist
Iris AO, Inc. - Twitter: @IrisAOMEMS

[cshahar]

Eric, here is Don's comments on the moon:

I don't remember ever using adaptive optics for the moon. I do have
some posted pictures, but the text says that the AO-2 was turned off.
Sorry, but astronomers can't figure out how to do adaptive optics with
extended objects. The large observatories are experimenting with a
multi-laser guide star system to essentially figure out how the
atmosphere looks like as a function of altitude and direction (like an
MRI scan), but that is way in the future.

Years ago, it was proposed and tested that sunspots could act like
"negative stars", but they did not get very far, and the solar
granulations only improved over a few arcseconds radius, using fast
image stabilization.

Sorry for the bad news, but adaptive optics is hard!

Don

[eroel]

Charles:
Well, I will try it anyway.
Eric.

[cshahar]

Great! Please let me know...

[Ewan]

Wouldn't an extremely fast frame rate camera achieve almost the same thing & probably is not that far off ?

[cshahar]

I wonder about that. I don't have enough technical knowledge to make a comparison, but I don't think the ground-based observatories would otherwise invest in such a system given that their advanced cameras are likely quite sophisticated. The SSM on the other hand offers another approach to the issue of seeing and is probably the best solution for amateurs. From the research I am doing I don't think an affordable, portable and easily usable AO system is available to amateurs just yet.

[fjabet]

I'm sorry to be the one who breaks your dreams apart, but there will be no AO for amateurs. Not in near future at least.

An AO for astronomy in a nutshell :

- Closed loop speed faster than seeing coherency time, ie above 500Hz at the very least
- Isoplanetism angle of a few arcsec : that means you can't correct more than that with a single star
- Ability to analyse PSF wavefront (night application) at >500Hz inside the isoplanetism angle. That means a lot of luck to have a bright star there, or using laser projection on the troposphere
- Ability to correct 1st+3rd order (tilt/focus/astig/coma/SA 3rd order). That means 7 mirrors on a diameter of the correction mirror.

So the product you mentionned is not an AO, neither is the SBIG tip tilt.

Frédéric.

[GaborKiss]

Frederic,

Then how do you see the future of planetary and solar imaging? Better cameras and higher FPS? In the last 10 years the quality of pictures are extremely evolving even without AO. The images 10 years back from the best locations are nowhere compared to the ones we can reach from under mediocre locations.

Regards,
Gabor

[cshahar]

Thanks Frédéric for that sobering assessment. I wanted to investigate the possibility but it turns out to be a dead end for now. Who would have predicted that astro-imaging technology progressed the way it did in the last 15 years? So we shall see what the future might bring.

-Charles

[solaman57]

I have been doing research on adaptive optics specifically for solar imaging. Adaptive optics are an indispensable tool for ground-based solar telescopes, enabling them to overcome adverse seeing conditions, so they can obtain diffraction limited views. In fact, they are credited with reviving ground-based solar astronomy since their inception. But these tools are more complicated to construct than the ones used for nighttime imaging, basically because of the difference between using stars (pinpoints) to measure how the light is distorted, versus large, low-contrast targets comprising an infinite number of point sources.

Unfortunately, there does not seem to be commercially available solar adaptive optics instruments yet. I was wondering if anyone has come across these types of instruments? It would seem less commercially viable since "serious" solar imagers / observers represent only a small percentage of those engaged in astronomical pursuits.

-Charles