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New Kind of blows holes in Ranting Ross did...
About Adaptive Optics being a waste of energy or some such bullshit.
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
New Actually, what he said was:
[link|/forums/render/content/show?contentid=80799|This.]
Regards,

-scott anderson

"Welcome to Rivendell, Mr. Anderson..."
New Munch is so appropriate for that post. :-)
New Wow, 100K posts ago... Dam.
Still blows holes in his response to AO.
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
New Not completely
His criticisms are still perfectly accurate. What this underscores is that for some things, sort of working is often good enough.

Adaptive optics needs a wavefront reference, usually a bright star right behind what you're looking at. Only 1% of the sky has adequate references. There are ways to put a fake one up (shine something up that will reflect off of a known depth in the atmosphere, and look at the reflection), but those do not work as well as natural ones. Besides, the technique introduces errors that need to be corrected (in visible wavelengths they can be corrected for for about 50% of the sky, in infrared you can correct for 90% of the sky).

Secondly it is frequency dependent. If you're looking at a range of wavelengths, the one that you're using for the guide will be dead on (at least very close to the wavefront reference) - and the rest will smear. The cause is the same thing that causes a prism to scatter a rainbow - different frequencies do different things in the atmosphere.

Thirdly you can't predict the turbulence. Although this point of his is really an explanation for the first, you still can't predict the turbulence. You can merely calculate how fast it is likely to change, and then you know how quickly you need to measure and adapt. The wavefront reference is what you measure from, and the speed of adaption needs to be on the order of 0.001 s.

For a pinpoint image of something like a planet, this is great. For squeezing extra performance out of a telescope this is also great. The technique is definitely worthwhile.

However Ross is dead right. If you could take the same telescope and put it above the atmosphere, you'd get far better results than you every could with adaptive optics. Furthermore you can get those results in many wavelengths at once, over a wide field of view.

Take the Hubble. It has a 2.4m mirror. The Keck telescope has a 10m mirror. From straight optical principles you'd expect the Keck telescope to be able to see things that are 16x the detail that the Hubble can see. (That is images whose height and width are each 1/4 of what Hubble can make out.) But no. Instead we are astounded that the Keck can focus on a single point in the sky with results that are somewhat better than the Hubble, in one wavelength at a time.

I don't mean to say that it isn't an impressive accomplishment. It is. It isn't simple and it takes a lot of work. There are applications where it can be useful. But just imagine what the Keck telescope could do if we could just place it where the Hubble is! Conversely things like the full color shots of nebulae that the Hubble is famous for will never be duplicated from the ground. (Unless they build that telescope in Antarctica...)

Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
New You mean the "artificially colored shots of nebulae"
===

Purveyor of Doc Hope's [link|http://DocHope.com|fresh-baked dog biscuits and pet treats].
[link|http://DocHope.com|http://DocHope.com]
New I think Ross is underestimating the cost of space-based
What with launches and maintenance.

If the Keck breaks down, it can be fixed immediately. Not so the Hubble or any other similar space telescope. The optics can also be built in the same gravity well that they are used in; constructing optics on Earth that deform in micro-gravity exactly how they need to is not a trivial problem at all.

While wide spectrum is good, a lot of astronomical observation is done in single wavelengths anyway. Once the AO technology is perfected, they should be able to do a cross-spectrum sampling quickly when needed.

As far as turbulence goes... the proof of the technique will be that it works. Which the photos of Uranus seem to indicate. Waving your hands around saying "it's hard!" doesn't mean squat when the pictures still come out.

But as you said, it's good enough.
Regards,

-scott anderson

"Welcome to Rivendell, Mr. Anderson..."
New Yes, but is it using good film?
===

Purveyor of Doc Hope's [link|http://DocHope.com|fresh-baked dog biscuits and pet treats].
[link|http://DocHope.com|http://DocHope.com]
New No.
They are using the 40MP/cm^2 CCD.

:)
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
New This is the whole thing I believe is blowing
the Holes in his rant about the whole AO thing.
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
New I don't think that Ross is estimating the cost at all
Let's get actual figures.

According to [link|http://www.noao.edu/system/tsip/keck_cost.html|http://www.noao.edu/...ip/keck_cost.html], the cost of Keck is $25 million per year counting the telescope depreciating over 20 years, and operational costs. So we're talking $500 million. In the last 2 years they averaged 544 observing nights per year (they have 2 telescopes). For a night of observing that comes out to $47,400/night. If you get 10 hours per night, that is 4,740/hour.

According to [link|http://hubble.nasa.gov/faq.html|http://hubble.nasa.gov/faq.html], Hubble cost $1.5 billion to launch, and $230-250 million/year. It launched in 1990, and will continue until later this decade. So its total cost is about $6 billion or so. That is spread out over about 20 years, so that is $300 million/year, or $34,209/hour.

So anything that the Hubble can do which can be done by the Keck should be done by the Keck instead.

However if the price of space flight can be brought down significantly (and I think that it probably can), then at some point space-based observatories will replace adaptive optics. Of course that point is not now, nor is it in the near future.

And in the meantime there are things that can only be done from space. Two of those things are deep-sky surveys of background radiation, and scans of random locations for very, very distant objects. I mention this because those surveys are of critical importance to cosmology, which ties in to fundamental physics, which is (of course) Danny's interest.

So while adaptive optics can do some things, it is of no use for the things that affect Danny. Worse yet, it replaces some of what space-based observatories are good for, which lessens the chance of getting better space-based observatories up there. So this technology worsens the future of astronomy from his point of view. Which I suspect is a reason that he is so strongly opposed to the technology.

Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
New It's a good reason.

Imric's Tips for Living
  • Paranoia Is a Survival Trait
  • Pessimists are never disappointed - but sometimes, if they are very lucky, they can be pleasantly surprised...
  • Even though everyone is out to get you, it doesn't matter unless you let them win.


Nothing is as simple as it seems in the beginning,
As hopeless as it seems in the middle,
Or as finished as it seems in the end.
 
 
New Yes, a good reason...
But the cost of space observatories, is saturating these budgets already. How can even he justify space based for only those two jobs known to really be effective in space... where as the bah-millions of other jobs that need to be done can be by earth-based.

Come on, what would *YOU* do skip?

Given your job is to bomb then hell out of the <insert target>

Make a down payment on a $1B Stealth Bomber only capable of dropping a few tons and make payments for $LOAN_LENGTH (longtime there bucko)

Buy a B-52 for a percentile fraction of that and run 10,000 sorties by the time you would have paid off the B2.
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
New But it isn't only those two jobs that Hubble is good for
There are a lot of jobs that Hubble is good for. The two that he cares about happen to be among them.

To pick another of more interest to you, if we want to some day carry out a comprehensive survey for major asteriods and comets of size over 1 km across that might be on an intersection path with us, then guess what, Hubble or relatives are the only way to do it. (If we know about something of this size a few decades ahead of time, we can probably do something about it.)

In other words adaptive optics is useless for the only astronomical survey that is likely to have defence implications for us.

Furthermore many people believe that it is possible to dramatically lower the cost of operating in space. In which case the economics against space-based telescopes would go away. And the same survey which was estimated as being a security issue becomes the groundwork to identify what space-based objects we might want to try to mine!

Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)
New Adaptive optics is what he was
talking about. And can adaptive optics do bah-millions of other jobs? I'm with him - space-based platforms are a better long-term investment.

Hell, it's a better investment even if it only gets us more practice in operating in space... WE HAVE TO GET OFF THIS ROCK.

Oh. Right. Space-based weapons will fill this role. No need for peaceful platforms in space. That would be a waste of money.


Imric's Tips for Living
  • Paranoia Is a Survival Trait
  • Pessimists are never disappointed - but sometimes, if they are very lucky, they can be pleasantly surprised...
  • Even though everyone is out to get you, it doesn't matter unless you let them win.


Nothing is as simple as it seems in the beginning,
As hopeless as it seems in the middle,
Or as finished as it seems in the end.
 
 
New Waste of money
Better spent on space telescopes and saving Hubble. Self-evident.

(BTW, I find it hilarious to find you taking me to task on a question of science. I had forgotten 100 times more than you'll ever know ages ago.)

I think I'm done with this board. I'm sick of you people.
-drl
Expand Edited by deSitter Nov. 15, 2004, 10:15:18 PM EST
New Take some time off, but please come back.
You know we enjoy teasing you. :-)

I think we've all learned a lot from you. Don't take our disagreements for lack of respect or affection. This would be a very boring place without you.

Cheers,
Scott.
New l8r.
--
[link|mailto:greg@gregfolkert.net|greg],
[link|http://www.iwethey.org/ed_curry|REMEMBER ED CURRY!] @ iwethey
No matter how much Microsoft supporters whine about how Linux and other operating systems have just as many bugs as their operating systems do, the bottom line is that the serious, gut-wrenching problems happen on Windows, not on Linux, not on Mac OS. -- [link|http://www.eweek.com/article2/0,1759,1622086,00.asp|source]
Here is an example: [link|http://www.greymagic.com/security/advisories/gm001-ie/|Executing arbitrary commands without Active Scripting or ActiveX when using Windows]
     You can't tell me this title wasn't intentional: - (admin) - (21)
         This title wasn't intentional. - (drewk) - (1)
             Nyuk, nyuk, nyuk. -NT - (Another Scott)
         Kind of blows holes in Ranting Ross did... - (folkert) - (17)
             Actually, what he said was: - (admin) - (13)
                 Munch is so appropriate for that post. :-) -NT - (Another Scott)
                 Wow, 100K posts ago... Dam. - (folkert) - (11)
                     Not completely - (ben_tilly) - (10)
                         You mean the "artificially colored shots of nebulae" -NT - (drewk)
                         I think Ross is underestimating the cost of space-based - (admin) - (8)
                             Yes, but is it using good film? -NT - (drewk) - (1)
                                 No. - (folkert)
                             This is the whole thing I believe is blowing - (folkert)
                             I don't think that Ross is estimating the cost at all - (ben_tilly) - (4)
                                 It's a good reason. -NT - (imric) - (3)
                                     Yes, a good reason... - (folkert) - (2)
                                         But it isn't only those two jobs that Hubble is good for - (ben_tilly)
                                         Adaptive optics is what he was - (imric)
             Waste of money - (deSitter) - (2)
                 Take some time off, but please come back. - (Another Scott)
                 l8r. -NT - (folkert)
         To reiterate - (deSitter)

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