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Old 19-02-2021, 11:03 PM
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Video on the ELT

Better than the James Webb Space Telescope?


The Upcoming Extremely Large Telescope

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•Feb 18, 2021









Looking forward to the James Webb Space Telescope? Just wait until ESO's Extremely Large Telescope (ELT) is completed.
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Old 20-02-2021, 06:33 AM
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Thanks for sharing that. It was a very enjoyable watch.

Best
JA
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Old 20-02-2021, 07:23 AM
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Quote:
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Thanks for sharing that. It was a very enjoyable watch.

Best
JA



Thanks - I thought it was good enough to subscribe to the channel.
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Old 20-02-2021, 02:31 PM
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Very good! Adaptive optics is incredible.
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Old 23-02-2021, 08:07 AM
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Very good! Adaptive optics is incredible.

I can't wait to see the pictures.
I'm wondering if the adaptive optics will only put
a picture in focus over a tiny area?
Hubble gives a larger area- the full frame -
compared to other adaptive pics I've seen
from ground telescopes.
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Old 23-02-2021, 08:26 AM
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Quote:
Originally Posted by alpal View Post
I can't wait to see the pictures.
I'm wondering if the adaptive optics will only put
a picture in focus over a tiny area?
Hubble gives a larger area- the full frame -
compared to other adaptive pics I've seen
from ground telescopes.
According to the info in the video, the 4th mirror in the telescope, the adaptive mirror has 8000 actuators and is 2.4m in diameter. So if those actuators are spread around the mirror, then there is every reason to expect that the adaptive optics will control its whole field and therefore help to maintain focus/sharpness across the field. That is not to say it would be easy especially at 1000 Hz.

It definitely will be a sight to behold in whatever it is.. 4years or so.

Best
JA
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Old 23-02-2021, 03:18 PM
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great video, would love to have one!
I would have called it ELD for extremely large dob!
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Old 24-02-2021, 02:41 PM
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Originally Posted by JA View Post
According to the info in the video, the 4th mirror in the telescope, the adaptive mirror has 8000 actuators and is 2.4m in diameter. So if those actuators are spread around the mirror, then there is every reason to expect that the adaptive optics will control its whole field and therefore help to maintain focus/sharpness across the field. That is not to say it would be easy especially at 1000 Hz.

It definitely will be a sight to behold in whatever it is.. 4years or so.

Best
JA



I don't know if that's true.
Information on the f ratios for the ELT is here:
https://www.eso.org/sci/facilities/e...escope/design/




I couldn't find any specification requirements for the adaptive optics here:
https://www.eso.org/sci/facilities/develop/ao/str.html




cheers
Allan
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Old 24-02-2021, 03:36 PM
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Hi Allan,

In the first link to the ESO in your most recent post (text quoted below) it mentions the 8000 actuators on the adaptive optics (achieved on the 2.4m diameter mirror M4). the same information is also stated in the initial Video.

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JA
"E-ELT OPTICAL DESIGN

The optical design for the E-ELT is that of a folded three-mirror anastigmat, folding being provided by two flat mirrors sending the beam to either Nasmyth foci along the elevation axis of the telescope (see Figure 1). The optics are mounted on an altitude azimuth telescope main structure.
The present concept features as a baseline for the primary mirror (M1) an elliptical f/0.93 segmented mirror of 39-m diameter and a 11.1-m central obstruction. The 4.2-m secondary mirror (M2) is convex and returns the beam, through a hole in the quaternary mirror (M4), to the 3.8-m mildly aspheric concave tertiary mirror (M3) located at the vertex of the primary. The beam is reflected by M3 to the adaptive optics system, the 2380x2340mm quaternary flat adaptive mirror M4, supported by up to 8000 actuators, and the fifth mirror in the train (M5) that allows for the final image correction. M4 is inclined at 7.75 degrees to the beam direction. M5 is a flat mirror, elliptical in contour, defines the altitude axis of the telescope and steers the beam towards the Nasmyth focus. The output beam at f/17.48 is very nearly diffraction limited over the entire 10-arcminute field of view. The total Nasmyth field of view is limited to 10 arcmin by the dimensions of the way-through hole in M4. The rather large Nasmyth focal ratio is constrained by the backfocal distance, and the location and size of mirrors M4 to M5."

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Old 25-02-2021, 06:17 PM
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Quote:
Originally Posted by JA View Post
Hi Allan,


The output beam at f/17.48 is very nearly diffraction limited over the entire 10-arcminute field of view.




Thanks -
that sounds like it will be a sharp image -
better than 0.1 arc seconds - (Hubble's resolution)

over the entire field of view.
I hope so.



cheers
Allan
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