Ground based telescopes have surpassed Hubble Space Telescope in picture sharpness

It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope. Ground telescopes have been much bigger than the Hubble Space telescope and could capture more light.

The MUSE Wide Field Mode coupled to GALACSI in ground-layer mode corrects for the effects of atmospheric turbulence up to one kilometre above the telescope over a comparatively wide field of view. But the new Narrow Field Mode using laser tomography corrects for almost all of the atmospheric turbulence above the telescope to create much sharper images, but over a smaller region of the sky.

The 8-meter UT4 reaches the theoretical limit of image sharpness and is no longer limited by atmospheric blur.

The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it passes through our atmosphere, and astronomers must use clever technology to improve image quality artificially.

To achieve this four brilliant lasers are fixed to UT4 that project columns of intense orange light 30 centimeters in diameter into the sky, stimulating sodium atoms high in the atmosphere and creating artificial Laser Guide Stars. Adaptive optics systems use the light from these “stars” to determine the turbulence in the atmosphere and calculate corrections one thousand times per second, commanding the thin, deformable secondary mirror of UT4 to constantly alter its shape, correcting for the distorted light.

MUSE is not the only instrument to benefit from the Adaptive Optics Facility. Another adaptive optics system, GRAAL, is already in use with the infrared camera HAWK-I. This will be followed in a few years by the powerful new instrument ERIS.

18 thoughts on “Ground based telescopes have surpassed Hubble Space Telescope in picture sharpness”

  1. I would be very concerned about those telescopes being high in the sky with sodium. If they get to high a number they might have to end up taking hydrochlorothiazide….:-))

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  2. Just want to point out… The statement… It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope. Depends very much on having a REALLY good viewing night to begin with (which still doesn’t ameliorate the atmospheric turbulence blurring effects entirely), AND having a relatively bright object (such as Neptune or Uranus) quite close to the artificial star that’s used to compute the counter-curve to correct for instantaneous aberration-at-a-distance effects. VERY nice picture of the planet. Very nice indeed. Now, let’s see how it does on a great big “10-Luna-diameter” low-brightness nebula with all sorts of “deep” detail. Oh, it doesn’t do that. Because it only corrects for turbulence near its artificial star. Of course. Just saying GoatGuy

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  3. I would be very concerned about those telescopes being high in the sky with sodium. If they get to high a number they might have to end up taking hydrochlorothiazide….:-))

    Reply
  4. Just want to point out…The statement…It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope.Depends very much on having a REALLY good viewing night to begin with (which still doesn’t ameliorate the atmospheric turbulence blurring effects entirely) AND having a relatively bright object (such as Neptune or Uranus) quite close to the artificial star that’s used to compute the counter-curve to correct for instantaneous aberration-at-a-distance effects. VERY nice picture of the planet. Very nice indeed.Now let’s see how it does on a great big 10-Luna-diameter”” low-brightness nebula with all sorts of “”””deep”””” detail. Oh”””” it doesn’t do that.Because it only corrects for turbulence near its artificial star.Of course.Just sayingGoatGuy”””

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  5. It has been a very good four decades for astronomy. I hope the next four decades will just be as fruitful. Still remember my first 31/2″ Edmunds refractor telescope with great fondness. In the backyard, freezing cold, looking at Saturn. Some of the best days of my life.

    Reply
  6. It has been a very good four decades for astronomy. I hope the next four decades will just be as fruitful. Still remember my first 31/2 Edmunds refractor telescope with great fondness. In the backyard freezing cold” looking at Saturn. Some of the best days of my life.”

    Reply
  7. Hmm, you may know more about this particular announcement than I do, GG, but at least one of your statements I’m pretty sure is out-of-date. Specifically, the need for a bright object “quite close to the artificial star”. In the early days of adaptive optics (AO), a bright object very close to the *target* star was needed for computing the dynamic corrections, but AFAIK that need went away with the use of artificial laser-generated guide stars. But you said “quite close to the artificial star”, so maybe there’s still a need for a second bright object (in addition to the laser guide star) to compute the dynamic corrections for the AO mirror. I’ve never heard that, but it would sorta make sense. With only one coherent source delivering enough photons per second to calculate wavefront distortions in real time, an approach that amounts to dithering would be needed. One can only calculate corrections to the extent that one can measure deviations. The deviations being sensed introduce a degree of blurring. Having two bright sources close together might allow more direct calculation of the wavefront distortions. But that’s what I gather this announcement was about. Four artificial guide stars in close proximity not only should allow faster and more direct calculation of the instantaneous wavefront distortions, but also perhaps allow a 3d model of refractive index variations within the atmosphere to be calculated. That sort of model would give the instantaneous corrections required at time X, but would also be predictive for the corrections for time X + delta X. The point spread functions for directions slightly off-axis could be calculated as well, giving a wider field of view for sharp imaging after image processing. So maybe extended objects *could* be sharply imaged. (Nothing as wide as the moon, I’m sure, but perhaps 10 arc-minutes?) The one thing that AO will never be able to do, regardless of telescope aperture, is image earth-like exoplanets. There’s a loss of

    Reply
  8. Hmm you may know more about this particular announcement than I do GG but at least one of your statements I’m pretty sure is out-of-date. Specifically the need for a bright object quite close to the artificial star””. In the early days of adaptive optics (AO)”” a bright object very close to the *target* star was needed for computing the dynamic corrections”” but AFAIK that need went away with the use of artificial laser-generated guide stars. But you said “”””quite close to the artificial star”””””” so maybe there’s still a need for a second bright object (in addition to the laser guide star) to compute the dynamic corrections for the AO mirror. I’ve never heard that but it would sorta make sense. With only one coherent source delivering enough photons per second to calculate wavefront distortions in real time an approach that amounts to dithering would be needed. One can only calculate corrections to the extent that one can measure deviations. The deviations being sensed introduce a degree of blurring. Having two bright sources close together might allow more direct calculation of the wavefront distortions.But that’s what I gather this announcement was about. Four artificial guide stars in close proximity not only should allow faster and more direct calculation of the instantaneous wavefront distortions but also perhaps allow a 3d model of refractive index variations within the atmosphere to be calculated. That sort of model would give the instantaneous corrections required at time X but would also be predictive for the corrections for time X + delta X. The point spread functions for directions slightly off-axis could be calculated as well giving a wider field of view for sharp imaging after image processing. So maybe extended objects *could* be sharply imaged. (Nothing as wide as the moon I’m sure but perhaps 10 arc-minutes?)The one thing that AO will never be able to do regardless of telescope aperture is image earth-like exoplanets. There’s a lo”

    Reply
  9. Not bad considering Hubble was launched back in 1990 with a 2.4 meter mirror, competing against modern 8 meter mirrors on the ground. Hubble can see near-UV, visible and near-IR waves. It’s replacement (James Webb Space Telescope) will be tuned to visible to mid-IR light. I imagine infrared is absorbed by the atmosphere and would be hard to duplicate that on the ground.

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  10. Not bad considering Hubble was launched back in 1990 with a 2.4 meter mirror competing against modern 8 meter mirrors on the ground.Hubble can see near-UV visible and near-IR waves. It’s replacement (James Webb Space Telescope) will be tuned to visible to mid-IR light. I imagine infrared is absorbed by the atmosphere and would be hard to duplicate that on the ground.

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  11. Not bad considering Hubble was launched back in 1990 with a 2.4 meter mirror, competing against modern 8 meter mirrors on the ground.
    Hubble can see near-UV, visible and near-IR waves. It’s replacement (James Webb Space Telescope) will be tuned to visible to mid-IR light. I imagine infrared is absorbed by the atmosphere and would be hard to duplicate that on the ground.

    Reply
  12. Hmm, you may know more about this particular announcement than I do, GG, but at least one of your statements I’m pretty sure is out-of-date. Specifically, the need for a bright object “quite close to the artificial star”.

    In the early days of adaptive optics (AO), a bright object very close to the *target* star was needed for computing the dynamic corrections, but AFAIK that need went away with the use of artificial laser-generated guide stars. But you said “quite close to the artificial star”, so maybe there’s still a need for a second bright object (in addition to the laser guide star) to compute the dynamic corrections for the AO mirror. I’ve never heard that, but it would sorta make sense. With only one coherent source delivering enough photons per second to calculate wavefront distortions in real time, an approach that amounts to dithering would be needed. One can only calculate corrections to the extent that one can measure deviations. The deviations being sensed introduce a degree of blurring. Having two bright sources close together might allow more direct calculation of the wavefront distortions.

    But that’s what I gather this announcement was about. Four artificial guide stars in close proximity not only should allow faster and more direct calculation of the instantaneous wavefront distortions, but also perhaps allow a 3d model of refractive index variations within the atmosphere to be calculated. That sort of model would give the instantaneous corrections required at time X, but would also be predictive for the corrections for time X + delta X. The point spread functions for directions slightly off-axis could be calculated as well, giving a wider field of view for sharp imaging after image processing. So maybe extended objects *could* be sharply imaged. (Nothing as wide as the moon, I’m sure, but perhaps 10 arc-minutes?)

    The one thing that AO will never be able to do, regardless of telescope aperture, is image earth-like exoplanets. There’s a loss of contrast range associated with the operation of the AO system, but more fundamentally, there’s light scattering in the atmosphere that can’t be circumvented by any ground-based instrument. The fancy coronagraphs that are planned for allowing space-based telescopes to reduce diffracted light intensity by the ten orders of magnitude needed to image earth-like exoplanets are useless for ground-based telescopes. They can’t suppress light that’s scattered within the atmosphere itself.

    Reply
  13. It has been a very good four decades for astronomy. I hope the next four decades will just be as fruitful. Still remember my first 31/2″ Edmunds refractor telescope with great fondness. In the backyard, freezing cold, looking at Saturn. Some of the best days of my life.

    Reply
  14. Just want to point out…
    The statement…

    It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope.

    Depends very much on having a REALLY good viewing night to begin with (which still doesn’t ameliorate the atmospheric turbulence blurring effects entirely), AND having a relatively bright object (such as Neptune or Uranus) quite close to the artificial star that’s used to compute the counter-curve to correct for instantaneous aberration-at-a-distance effects.

    VERY nice picture of the planet.
    Very nice indeed.

    Now, let’s see how it does on a great big “10-Luna-diameter” low-brightness nebula with all sorts of “deep” detail.

    Oh, it doesn’t do that.
    Because it only corrects for turbulence near its artificial star.

    Of course.
    Just saying

    GoatGuy

    Reply
  15. I would be very concerned about those telescopes being high in the sky with sodium. If they get to high a number they might have to end up taking hydrochlorothiazide….:-))

    Reply

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