I gotta say I'm quite jealous of your dark skies and beautiful photography.
Also, how are you overcoming flexure and mirror flop with your setup!? I have troubles keeping a 6" stable for a minute with a reasonable mount. Do you have more info on your setup anywhere?
I see this question a lot. I used to have an obsession with 'true color'; images felt fake otherwise. Artificial.
I'm a working scientist now, and my view has changed. I realize how limited our senses are. How much of the world--of the universe--I'd miss by restricting it to just what my eyes can see natively. Even among colors that I can see, but perhaps the signal is too faint ... I'm a lot more tolerant of color-mapped images now. I don't see them as artificial anymore, but as beautiful and transcendental. A window into a hyper-spectral world normally invisible to me. It's really something special. I wish I could share this perspective with more people.
The advantage of MUSE is that you get all color information, i. e. the flux at any wavelength from blue to red.
In principle, one can use this together with the sensitivity curve for our eyes to construct a natural image.
In this case, I think, they tried to imitate the color scheme from the Hubble image which is more limited.
In short: Not sure how realistic this is, but one could make a realistic image from the new data.
> With this new capability, the 8-metre UT4 reaches the theoretical limit of image sharpness and is no longer limited by atmospheric blur.
Theoretical limit as in diffraction limited? How will this technology "scale" to other frequencies and resolutions? Related to this diffraction limit: is there any overlap in the advances in microscopy and astronomy? For example, do advances in super-resolution microscopy[0] affect advances in optics in astronomy? Could advances in adaptive optics in astronomy somehow translate to microscopy?
(I'm also curious if this technology will make putting telescopes in satellites not worth the cost, but that question was already asked and answered here: https://news.ycombinator.com/item?id=17557482)
Yes, the diffraction limit is meant here. The VLT has four 8 m mirrors, for each of them the angular resolution limit is = wavelength/diameter = 8 * 10^(-8) rad.
The practical resolution of the new narrow-field mode is about 4*10^(-7) rad, and it was one order of magnitude larger before.
Adaptive optics is the key invention here. As far as I know, it works better in the near-infrared than in the red part of the optical range, and it gets worse toward the blue part. Due to this, our resolution changes as a function of the wavenlength, since MUSE captures the flux from all wavelengths at the same time.
It's funny that your mention super-resolution microscopy because Stefan Hell, one of the Nobel Prize winners for advances in that field, works in the same city as we do. So far, I don't think we have any overlap with what he does.
In my first year of grad school (1995) our microscopy professor showed us an astronomy adaptive optics paper and said "we're going to do that". Years later, they did that.
We can achieve a very high resolution from the ground but only in a very small field of view. To cover one typical HST image with MUSE at the VLT, we would need a mosaic of hundreds of exposures.
The reason for this are the four artificial guiding stars from the lasers. The closer they are together on the sky, the more atmospheric distortion you can correct.
Some parts of the electromagnetic spectrum are also not possible to observe from the ground. That's mainly UV and shorter wavelengths (X-ray, gamma-rays). We will always need space telescopes if we want to have these photons.
Adaptive optics is really only effective in the infrared. And really only in the near-infrared, as past 5 microns, we can't really see through the atmosphere. In the visible, ground-based can't match space observatories (in the visible, the atmospheric turbulence is way harder to correct for).
In those pictures of neptune, what is the KM-per-pixel were looking at?
Is there a minimum focal length on this? Purely hypothetical: Could we basically see astronaut's footprints on the moon with this? What about looking into the window of the ISS?
In this narrow-field mode of MUSE, the CCD detector can resolve 0.025 arcseconds per pixel (arcsecond is a weird unit for angles used in astronomy). At the current distance to Neptune (according to wolframalpha: about 30 au = 4.5 bn km), this corresponds to about 500 km/px.
Due to observing conditions, I think the real resolution was more like 0.07...0.08 arcseconds, so maybe it was 1000 to 2000 km/px.
I'm not sure if the focal length plays any role here. The resolution is usually limited by the telescope size (true for all telescopes, scales with 1/diameter) and atmospheric conditions (only relevant for ground based ones). At the distance of the moon (300,000 km), the physical resolution is 36 m/px and for the ISS (400 km) it is 5 cm/px.
If you want to play around with it, here's the formula:
length_still_resolved = angular_resolution * distance
The angular resolution is 1.2 * 10^-7 (= 0.025 arcseconds converted to radian), distance and length_still_resolved have the same units.
> Q: Could the VLT take a picture of the Moon-landing sites?
> A: Yes, but the images would not be detailed enough to show the equipment left behind by the astronauts. Using its adaptive optics system, the VLT has already taken one of the sharpest ever images of the lunar surface as seen from Earth: http://www.eso.org/public/news/eso0222/. However, the smallest details visible in this image are still about one hundred metres on the surface of the Moon, while the parts of the lunar modules which are left on the Moon are less than 10 metres in size. A telescope 200 metres in diameter would be needed to show them. [continued]
Can you tell us about your favourite globular clusters? I know some of them have very interesting properties like having similar stellar ages but are there any really peculiar ones you can tell us about? Also, I'd love to see some of the images your referring to.
I like NGC 3201 because we found a stellar mass black hole in it (https://www.eso.org/public/news/eso1802/). There should be many more of them in all clusters, but they are hard to find. Theorists can use this to check their N-body simulations of globular clusters.
Some clusters (omega Cen, 47 Tuc) are really weird and different from all others. We think that they might be the remnant cores of dwarf galaxies.
anon1253|7 years ago
All kidding aside, do you think there is some scientific value in the efforts of hobby astronomers and astrophotographers around the world?
zfedoran|7 years ago
Also, how are you overcoming flexure and mirror flop with your setup!? I have troubles keeping a 6" stable for a minute with a reasonable mount. Do you have more info on your setup anywhere?
Jaruzel|7 years ago
Osmium|7 years ago
I'm a working scientist now, and my view has changed. I realize how limited our senses are. How much of the world--of the universe--I'd miss by restricting it to just what my eyes can see natively. Even among colors that I can see, but perhaps the signal is too faint ... I'm a lot more tolerant of color-mapped images now. I don't see them as artificial anymore, but as beautiful and transcendental. A window into a hyper-spectral world normally invisible to me. It's really something special. I wish I could share this perspective with more people.
eisstrom|7 years ago
In short: Not sure how realistic this is, but one could make a realistic image from the new data.
modzu|7 years ago
https://upload.wikimedia.org/wikipedia/commons/6/63/Neptune-...
vanderZwan|7 years ago
Theoretical limit as in diffraction limited? How will this technology "scale" to other frequencies and resolutions? Related to this diffraction limit: is there any overlap in the advances in microscopy and astronomy? For example, do advances in super-resolution microscopy[0] affect advances in optics in astronomy? Could advances in adaptive optics in astronomy somehow translate to microscopy?
(I'm also curious if this technology will make putting telescopes in satellites not worth the cost, but that question was already asked and answered here: https://news.ycombinator.com/item?id=17557482)
[0] https://en.wikipedia.org/wiki/Super-resolution_microscopy
eisstrom|7 years ago
Adaptive optics is the key invention here. As far as I know, it works better in the near-infrared than in the red part of the optical range, and it gets worse toward the blue part. Due to this, our resolution changes as a function of the wavenlength, since MUSE captures the flux from all wavelengths at the same time.
ESO wants to achieve an even higher resolution at the 40m Extremely Large Telescope (another order of magnitude better): https://www.eso.org/public/teles-instr/elt/
It's funny that your mention super-resolution microscopy because Stefan Hell, one of the Nobel Prize winners for advances in that field, works in the same city as we do. So far, I don't think we have any overlap with what he does.
dekhn|7 years ago
appleflaxen|7 years ago
is that true? does this mean that we should simply use ground-based 'scopes with adaptive optics?
eisstrom|7 years ago
Here is an image of them: https://www.eso.org/public/unitedkingdom/images/vlt-laser-cc...
Some parts of the electromagnetic spectrum are also not possible to observe from the ground. That's mainly UV and shorter wavelengths (X-ray, gamma-rays). We will always need space telescopes if we want to have these photons.
Tepix|7 years ago
semaphoreP|7 years ago
mattlondon|7 years ago
In those pictures of neptune, what is the KM-per-pixel were looking at?
Is there a minimum focal length on this? Purely hypothetical: Could we basically see astronaut's footprints on the moon with this? What about looking into the window of the ISS?
eisstrom|7 years ago
I'm not sure if the focal length plays any role here. The resolution is usually limited by the telescope size (true for all telescopes, scales with 1/diameter) and atmospheric conditions (only relevant for ground based ones). At the distance of the moon (300,000 km), the physical resolution is 36 m/px and for the ISS (400 km) it is 5 cm/px.
If you want to play around with it, here's the formula: length_still_resolved = angular_resolution * distance
The angular resolution is 1.2 * 10^-7 (= 0.025 arcseconds converted to radian), distance and length_still_resolved have the same units.
m-app|7 years ago
> Q: Could the VLT take a picture of the Moon-landing sites?
> A: Yes, but the images would not be detailed enough to show the equipment left behind by the astronauts. Using its adaptive optics system, the VLT has already taken one of the sharpest ever images of the lunar surface as seen from Earth: http://www.eso.org/public/news/eso0222/. However, the smallest details visible in this image are still about one hundred metres on the surface of the Moon, while the parts of the lunar modules which are left on the Moon are less than 10 metres in size. A telescope 200 metres in diameter would be needed to show them. [continued]
arriu|7 years ago
Thanks!
eisstrom|7 years ago
Some clusters (omega Cen, 47 Tuc) are really weird and different from all others. We think that they might be the remnant cores of dwarf galaxies.
What images do you mean?