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Uranus cloud bands in a C8

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#51 stanislas-jean

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Posted 25 October 2012 - 12:03 PM

Searching on the net I found this
http://www.planetary...eck-photos.html
The pictures are the same but the performance dates are different.
Good read.
Make trials still Eddgie, the more conspiscious features are the dark north hemiphere and the lighted thin equatorial zone. Question also of light level at the eyepiece, the optimum magnification is to be researched.
Stanislas-Jean
 

#52 stanislas-jean

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Posted 28 October 2012 - 04:24 AM

An Uranus report of last 27th performed with the 305mm cassegrain.
Only average conditions for the best momments.
The yellow filter was welcome for capturing the overall pattern of the Urannus, but with difficulty.
For your perusal.
Stanislas-Jean

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#53 Asbytec

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Posted 28 October 2012 - 04:28 AM

You got some crazy eyes, Stanislas...amazing.
 

#54 telescopemullet

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Posted 28 October 2012 - 10:56 AM

Nothing amazing about it, same story, still not believable.
 

#55 stanislas-jean

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Posted 28 October 2012 - 11:32 AM

thanks for your restricted vocabulary.
Still on stand=by!
Stanislas-Jean
 

#56 Cotts

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Posted 28 October 2012 - 05:03 PM

Stan, your drawings do not show the same curvature of the features as they are in the Keck pictures. In most of your sketches you show the 'bands' to be nearly straight lines and never even remotely as curved as they are in reality. This, plus your continiung failure to show the limb darkening in your sketches, reduces greatly the credibility of your efforts.

Dave
 

#57 azure1961p

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Posted 28 October 2012 - 06:42 PM

The lack of the limb darkening does remove any kind of measure by which to gauge the more subtle features. It makes no good sense to omit this much needed standard as a jumping off point for the finer subtleties. Yes, its a given that the limb shadow is ALWAYS there but being that its ALWAYS needed as a judgement rule, the omission is peculiar.

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#58 stanislas-jean

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Posted 29 October 2012 - 02:05 AM

Thanks for your interrest here.
You see the lack of limb darkening can be added, because well seen but this bring what?
If you hope to compare the darkening intensity with some albedo variations noted on "bands", I think you are too demanding.
This is just an intellectual requirement that hope to perform what is not possible to perform.
See the "thickness" of this darkening edge, this take say .2-.3" of arc against a disk of 3.66" of arc where the wider band is about 1-1.2" of arc width, the size of some albedo variations of around 1" of arc and slightly less.
You are too demanding and I think you cannot imagine the difficulty for the least to catch such amount at final.
Showing the limb darkening is peanut against the rest of the sketch. If the credibility is quoted only by this fact I am sorry this is not enough.
However the next documents will have for closing this kind of discussion that doesnot enter for moment of the real subjects that are Uranus presents variabilities and average aperture can be used on this subject.
It is not a matter to make direct comparison with keck results (you see the amount of features collected!).However the document is the reference document and well better than those published recently by some people happy to catch banding with pure circles shape.
But from this to see what can be in common: banding system, band edges not perfectly circular, physically impossible, albedo variations into the pattern, so many clear spots, the polar cap never seen as before that may be the collector of the spots, etc...).
What keck shows if in IR, 1.6µm, what we try to show is visual in red channel where the patterns are not reasonably the same.
Now we try to make something after building a method of observation, visually.
Anybody can be not in agreement, this is a fact and this is, but it cannot be discarded like this so easily.
Anybody also has to make a little effort for trying to understand with pro and cons arguments and not to reject only because not corresponding to their own views or disturbing somebody in high place.
I will continue to issue here some own documents with the demanded limb darkenings necessary, well observed.
Stanislas-Jean
 

#59 azure1961p

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Posted 29 October 2012 - 05:44 PM

"this bring what?"

Nothing at all Stan. Nothing at all.

Pete
 

#60 Asbytec

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Posted 29 October 2012 - 09:27 PM

I know this has been mentioned before, but how far into the infra red might one need visual acuity to see such bands? It's certainly a very rare ability. Eddgie and I, and many others, have failed to notice any features on Uranus while a couple observers must have "crazy eyes" or an active imaginations.

Stanislas mentioned the bands imaged in the far infrared are probably unchanged in the near infra red much closer to and probably right at the limit of human abilities. That argument makes some sense. But, not sketching limb darkening, well...yea, that's a curious omission. It should be there, but that its not might just be observer preference.

So, either Stanislas is seeing these things and truly gifted with "crazy eyes" (even filtered) or has an active imagination. Personally, I don't know which - just understand it's impossible for the vast majority of folks to observe those bands. If it were easy or could be done at all, surely more folks would report such observations.
 

#61 azure1961p

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Posted 29 October 2012 - 09:43 PM

Norme those Uranian festoons in the Keck images are wild. Its a hellish looking place despite the poker face it presents visually. Those festoons are so incredibly even and symmetrical.

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#62 Rick Woods

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Posted 29 October 2012 - 10:06 PM

Stan, your drawings do not show the same curvature of the features as they are in the Keck pictures. In most of your sketches you show the 'bands' to be nearly straight lines and never even remotely as curved as they are in reality. This, plus your continiung failure to show the limb darkening in your sketches, reduces greatly the credibility of your efforts.

Dave


Dave, I don't agree. Stan's belts appear to me to be curving in the same general way as the Keck pictures. Naturally they're not a perfect match; this is a very difficult observation at best. And, Stan has already said he deliberately doesn't include the limb darkening. I don't understand why that's such a big deal.
Can't anyone accept his observations for what they are - his observations? A couple of others have reported seeing features on Uranus without getting the treatment Stan is getting here.
God help him if he ever reports using Brandons! :shocked:
 

#63 Cotts

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Posted 29 October 2012 - 10:15 PM

Here's a screen grab of a typical Stan rendering of the belts/zones on Uranus. There's virtually zero curvature....

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#64 Cotts

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Posted 29 October 2012 - 10:19 PM

And here's a screen grab of the Keck IR shot which shows the amount of curvature that should be there assuming the bands/zones Stan is drawing are parallel to the equator of Uranus which they pretty much must be...

No resemblance.

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#65 starrancher

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Posted 29 October 2012 - 10:36 PM

Think there might be a slight difference in a Keck IR shot and what can be detected with a backyard scope through an eyepiece .
Seems some just need someone to bash and hate all the time .
 

#66 Asbytec

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Posted 30 October 2012 - 12:03 AM

Pete, hellish, yea....but I would give my left nut (since I don't use it much, anymore) to go there. Heck, to see it that well.

Personally, I cannot account for the differences between keck at 1.6 micrometers and visual at the limit of the human eye.

If anyone can see bands on Uranus, it's an amazing thing. An amazing, rare ability. So many simply cannot, myself included. Best I can make out is limb darkening and some tricky, random albedo changes probably induced by seeing...and trying and really wanting to see bands on Uranus.
 

#67 stanislas-jean

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Posted 30 October 2012 - 01:50 AM

I donot understand why people doesnot go to the spectrum given at the begin or the middle of this forum where the possible methane absorption bands appears, in visual field and NIR field with an evaluation of the possible contrast level. That's it. This is more constructive than intellectual observations (Pete) or by strict comparison (feature to feature with Cotts). All are not on the needed wave.
Curvature of banding system, you are too demanding with regards the kind of views we have. I remind here that most of the imagers happy to report banding system shows straight bands also (see the alpo japanese site). We report what we see and it is needed big apparent sizes observed for collecting such apart around the pole that is more evident.
The documents that you see on the forum are performed directly from the eyepiece, they are raw data not improved after at the desk, so some "features" may appear resulting of the paper surface quality or a pen a little too pushed.
We are at an epoch where avery thing must be perfect where this is not possible and not existing.
Festons on the sketch, I never wrote this word, never, this is your imagination that read, not your eyes.
Everything is difficult to collect and the sketch you remind, Cotts, is may be the better one that i did on Uranus and easily performed with excellent sky conditions.
Frankly it stuns me still, after I saw the keck images.
A new time, Images in IR will not be quite the same even with the similar resolution level in visual field (essentially the R channel). Because the interrested atmosphere layers in each are not the same because the atmosphere is scattering the light also.
A new time nobody is able to catch light above say 0.7µm, for convincing you, if this is not done, you can heat a piece of steel at different temperature and test your eyes, you will see. This is not a matter of superhumans but matter of training and lot lot lot of tests. Did you test yourself? Did you test the pertinence of your observational method (even imagers)?
I think not.
Stanislas-Jean
 

#68 Cotts

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Posted 30 October 2012 - 08:06 AM

I was referring to the curvature only. I know the detail in the Keck images would not be visible to Stan. My point is his ignoring this curvature (which would be in any bands parallel to Uranus's equator) in his sketches.

Dave
 

#69 telescopemullet

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Posted 30 October 2012 - 10:00 AM

There's no hate going on here. He is posting drawings and touts them as being "real." Others can post that what he is drawing is imaginary. That's not hating; it's posting an informed and rationale difference of opinion, which just happens to be well cemented in fact.
 

#70 stanislas-jean

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Posted 30 October 2012 - 10:37 AM

without any argument.
just free opinions.
Stanislas-Jean
 

#71 stanislas-jean

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Posted 30 October 2012 - 10:51 AM

Cotts, you should consider the fact that at the eyepiece the apparent size of the planet stands between 20 and 26 minuts of arc only for me and my means. We need 500x to catch Uranus with the same size as the moon viewed with the nake eye.
Try to do some visual tests on a sketch drawn in order to see them with the same angular size (a sketch with bands having the same curvature ratio). You will touch the difficulty that is not intellectual but physical.
It is honestly possible to apraise this curvature near the pole, so difficult at the equator, conditions needs to be perfectly excellent.
We can also draw with curvatures because softwares give the general pattern of the planet as lot of observers does on Mars for instance for the general pattern in use, but, is it well the right method?
Stanislas-Jean
 

#72 Rick Woods

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Posted 30 October 2012 - 02:16 PM

And here's a screen grab of the Keck IR shot which shows the amount of curvature that should be there assuming the bands/zones Stan is drawing are parallel to the equator of Uranus which they pretty much must be...

No resemblance.


I'm sorry, Dave; but I see a strong resemblance.

Edit: I notice there's no limb darkening in the Keck image, either.
 

#73 David Knisely

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Posted 30 October 2012 - 02:32 PM

Observing detail on Uranus is difficult in almost any telescope, especially with apertures smaller than 10 inches. That tiny disk and the powers needed to get it up to a decent size really strains the eye's ability to accurately detect any true detail which might be present without the eye/brain's own "noise" problems messing things up. Over the past 30+ years, I have viewed Uranus in 8 inch, 9.25 inch, 10 inch, 14 inch, 16 inch and 24 inch apertures under seeing conditions which should have allowed the detection of significant detail. Other than the limb darkening (which is quite easy to see even in modest apertures), I have never seen anything else on the disk with any of the previously mentioned telescopes. During recent observations which were triggered by some reports of alleged detail here in the planetary forum, in my 14 inch Newtonian at from 471x to nearly 600x, the disk appeared almost Q-ball smooth with a pleasant light bluish color. I will not dismiss the sudden temporary appearance of detail on that planet from time to time, but at least from my experience, I'm afraid that I am somewhat skeptical about routine visual detection of much band or spot-like detail on Uranus. Clear skies to you.
 

#74 stanislas-jean

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Posted 31 October 2012 - 01:27 AM

The main parameter is not the diameter but the contrast transfer ratio for capturing details of low contrasts (probably 1-2% level on the planet, not at the eyepiece).
A new time a 16" will not involve 2 times better the contrast level at the eyepiece with comparison of a 8".
Until your scopes at not characterised (PTV, RMS, etc... for getting a strehl not by a zygo report) this is useless.
Stanislas-Jean
 

#75 David Knisely

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Posted 31 October 2012 - 07:00 AM

The main parameter is not the diameter but the contrast transfer ratio for capturing details of low contrasts (probably 1-2% level on the planet, not at the eyepiece).
A new time a 16" will not involve 2 times better the contrast level at the eyepiece with comparison of a 8".
Until your scopes at not characterised (PTV, RMS, etc... for getting a strehl not by a zygo report) this is useless.
Stanislas-Jean


Sir, are you challenging my observations? The main parameter for determining the visibility of detail *is* the aperture used and only the optical quality may be second to that. Uranus is dim and small, so the more aperture one has, the better off one generally is. As for quality, I know precisely how good the optics are in my instruments (especially my 10 inch and 14 inch Newtonians, as I have actually had their figures measured). The 10 inch f/5.6 (custom figured by Enterprise Optics) has a p-v wavefront error of about 1/19.7 wave sodium light (4.1 nm RMS surface error or 1/67th wave RMS on the wavefront tested over seven zones) and a corresponding Strehl ratio of 0.991. In deference to Mike Lockwood, I have been asked by him not to disclose the precise figures for my 14 inch f/4.6 primary mirror that he refigured for me. However, suffice it to say that they are even better than the accuracy figures for my 10 inch Newtonian's mirrors. Mike refigured both the 14 inch primary and the 80mm (3.15 inch) secondary to a high degree of custom quality. I consider both mirrors in my 14 inch to be as good as can be obtained from *any* custom mirror maker, and they have proved their quality numerous times on the moon, the planets, and the deep-sky. My 10 inch f/5.6 Newtonian has a secondary obstruction of 21.4% of the aperture and my 14 inch f/4.6 Newtonian has an obstruction of 22.5%, so both obstructions are quite modest, especially when compared with some Cassegrain systems. The 16 inch I used to view Uranus with was at Lake Afton Observatory near Wichita, Kansas, and is a research grade Ritchey-Chretien used for research at Wichita State University as well as for viewing by the general public. The 24 inch Starmaster Newtonian I used to view Uranus at the Nebraska Star Party also had custom mirrors in it as well.

Any objection to a negative observation of detail on the disk of Uranus based on some alleged lack of optical quality figures presented is ridiculous. As I have clearly stated, from my observations (especially with this season's observations), I remain skeptical of claims of routine visual sightings of significant detail on the disk of Uranus. This is not "useless" but is a valid observation. Clear skies to you.
 






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