<p>I have read that one drawback of Adaptive Optics (AO) IFU observations is that they have lower SNR (compared natural seeing observations) and as a result it is harder to observe faint structures. For example, in a galaxy observation, while AO can give great resolution in the inner parts of the galaxy, the faint outskirts or the disk are more visible with natural seeing observations. Is that true? Why AO are not good with faint structures? I assume there is some loss of light during the whole process involved with AO which results in lower SNR? Can someone give me more details please?</p>

<p>EDIT1:</p>

<p>In this paper: <a href="http://adsabs.harvard.edu/abs/2011A%26A...528A..88G" rel="nofollow noreferrer">http://adsabs.harvard.edu/abs/2011A%26A...528A..88G</a> The authors say: </p>

<blockquote>
  <p>In the galaxies from the LSD sample we find more complex morphologies
  which are likely the consequence of the AO-assisted observations
  providing higher spatial resolution (∼0.2''FWHM) which allows us to
  spatially resolve more complex structures, but lower sensitivity to
  extended sources given the higher surface brightness detection
  threshold.</p>
</blockquote>

<p>Which implies that the AO are causing lower sensitivity. Maybe the lower sensitivity has something to do with the brightness of the laser used in the AO observations?</p>

CC BY-SA 3.0
2017-02-14T13:36:52.253Z
Please provide links to your sources.  As someone who spent 20 years designing and implementing AO systems, I might be able to comment if I knew more about the specific system in question.  Fundamentally I can say that an AO system corrects everything within its volume-corrected atmospheric region equally and that total light collection depends on a lot of factors.
Carl Witthoft
CC BY-SA 3.0
2017-02-14T21:46:41.890Z
Adding to the previous comment, it might be that the problem is not the AO but the IFU part. An IFU, is, IIRC, a spectrograph in each of its pixels. That will of course cost some signal. Also, these things are normally quite low resolution, so I don't know why you'd combine that with AO? Please clarify!
Alex
CC BY-SA 3.0
2017-02-23T12:12:10.043Z
Hi guys, sorry for the late reply. To be honest this is a belief that was built up in my head over time. I just took it as a fact and never questioned it for some reason. I managed to find a paper that claims the same thing. I will edit my original question now to include it.
AstrOne
<galaxy><adaptive-optics>
Adaptive Optics observations worse than natural seeing observations for faint structures?
AstrOne
# Adaptive Optics observations worse than natural seeing observations for faint structures?

(Asked by: username_0 on 2017-02-14)

I have read that one drawback of Adaptive Optics (AO) IFU observations is that they have lower SNR (compared natural seeing observations) and as a result it is harder to observe faint structures. For example, in a galaxy observation, while AO can give great resolution in the inner parts of the galaxy, the faint outskirts or the disk are more visible with natural seeing observations. Is that true? Why AO are not good with faint structures? I assume there is some loss of light during the whole process involved with AO which results in lower SNR? Can someone give me more details please?

EDIT1:

In this paper: <http://adsabs.harvard.edu/abs/2011A%26A...528A..88G> The authors say:

> In the galaxies from the LSD sample we find more complex morphologies
> which are likely the consequence of the AO-assisted observations
> providing higher spatial resolution (∼0.2''FWHM) which allows us to
> spatially resolve more complex structures, but lower sensitivity to
> extended sources given the higher surface brightness detection
> threshold.

Which implies that the AO are causing lower sensitivity. Maybe the lower sensitivity has something to do with the brightness of the laser used in the AO observations?

**Tags:** galaxy, adaptive-optics
> **Comments:**
> **username_1**: Please provide links to your sources.  As someone who spent 20 years designing and implementing AO systems, I might be able to comment if I knew more about the specific system in question.  Fundamentally I can say that an AO system corrects everything within its volume-corrected atmospheric region equally and that total light collection depends on a lot of factors.  
> **username_2**: Adding to the previous comment, it might be that the problem is not the AO but the IFU part. An IFU, is, IIRC, a spectrograph in each of its pixels. That will of course cost some signal. Also, these things are normally quite low resolution, so I don't know why you'd combine that with AO? Please clarify!  
> **username_0**: Hi guys, sorry for the late reply. To be honest this is a belief that was built up in my head over time. I just took it as a fact and never questioned it for some reason. I managed to find a paper that claims the same thing. I will edit my original question now to include it.  

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## 0 answers

