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Uranus cloud bands in a C8

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#1 Eddgie

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Posted 16 September 2012 - 09:08 AM

I don't know if the person that did these drawings posted them here, but I just saw them.

A month ago or so there was a thread talking about observing details on Neptune and Uranus, and I had mentioned that I have seen features on these planets in the past using my C14.

I had the senses that there may have been some skepticism, because these features are generally very low contrast.

But this link has a drawing that someone made showing detail on Uranus (!) using.. Drum-roll please... An 8" SCT!

Bravo!

Detail on Uranus using an 8" SCT.. Confirmed by Peach image using a C14!
 

#2 JimK

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Posted 16 September 2012 - 09:16 AM

Wow! Thanks for posting the link. A new goal to attain for planetary observers. Very impressive.
 

#3 John Boudreau

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Posted 16 September 2012 - 10:28 AM

Damian's image was taken with a 685nm longpass filter. One simply cannot confirm a visual observation with an image taken in near-IR light.

Damian (and others including myself), have not been able to capture these features in visible light. Damian mentions that himself in the text accompanying the image that you've linked to.
 

#4 stanislas-jean

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Posted 16 September 2012 - 12:25 PM

We will not retake the forum about Uranus but frankly John if imagers are not showing something in RGB doesnot mean there is nothing in visual fields.
This means only the capability is not enough using the method employed.
Now what is shown in near nir will not differ substantially from the visual field.
We can say an happy coincidence and there are someothers also.
This needs more analysis being not black and white difference.
Stanislas-Jean
 

#5 stanislas-jean

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Posted 16 September 2012 - 12:54 PM

There are here observations performed with the 150mm refractor that is a little more contrasty than the C8.
Stanislas-Jean

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#6 David Knisely

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Posted 16 September 2012 - 12:59 PM

Yes, but it was taken with a deep red filter (685nm Infrared filter) and was the result of around 45 minutes of taking multiple individual frames (stacked and probably heavily processed to boot). It was also taken with a 14 inch aperture, which would have a much better chance of resolving significant detail on the planet than an 8 inch would. I would be willing to bet that if Damian Peach had used a broad V-band filter, the disk would be pretty blank. There is a BIG difference between visual observing and imaging the planet in the near infrared. Visually, I still do not see anything of note on the disk of Uranus (other than limb darkening), and most people probably won't see a lot more than that either. Clear skies to you.
 

#7 Eddgie

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Posted 16 September 2012 - 02:19 PM

And I can say that while not done on the same nights, these drawings (both in the C8 and 6" refractor) show a similar appearence to what I have observed visually using the C14.

I detect them as very slight shading differences between the polar areas and the equitorial areas. A faint contrast difference, but distinct enough that I am sure that I have seen them.

Drawings cannot always convey the subtle nature of these shadings, and sometimes, I think the camera may struggle to render them.

Camera's excel at capturing the smallerst angular detail, but I know from imaging and visual observing that sometimes color contrasts are not well rendered by a camera, and processing can further shift the result.

If the person doing the image cannot see the detail visually (because perhaps they have not tried to see it visually), then how can they know that their processing isn't obscuring some detail? Regisax and other programs can do very funny things to color shading during processing. I know this from direct experience. I don't image much because I am a very avid visual observer, but I do in fact image.

Anyway, I know I have seen it, and I totally believe these drawings and am happy to see that someone else has detected these, and in an aperture that is smaller than I would have thought capable of doing so. And I have every reason to trust these drawings because I have seen Urnaus with similar levels of detail.

Excellent. Really superb. High 5.
 

#8 Rick Woods

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Posted 16 September 2012 - 07:36 PM

This surprises me not at all. Good find!
 

#9 azure1961p

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Posted 16 September 2012 - 08:33 PM

I think the very healthy thing that comes out of all this is the controversey itself. And its not newbees versus vets - theres seasoned individuals on both sides of the aisle. The such a strong spirited opinion can be had in both camps sais a lot about the sensitivety of the observers for a fairly *dark* world that appears not so much bigger than Ganymede. Visual planetary observation is clearly a detail oriented pursuit and this - continued topic - is fine testament.

No matter what we may ultimately think, the whole question of real or not has heightened our awareness of this -out-of-the-way - world. I dont think Ill ever look at it again the same frankly, details or not.

The *other* post had some remarks out of bounds but in the interest of discussion and awareness its a winner thread.

My 10 cents.

Pete
 

#10 blb

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Posted 16 September 2012 - 08:50 PM

Personally I did not think that the other thread got out of bounds. Spirted debate sometimes gets a little loud but no blows were exchanged. I thought the mod should never have locked it. I too think we all were learning something that, like you said, will change the way we see Uranus in the future.
 

#11 Cotts

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Posted 16 September 2012 - 09:43 PM

It seems Stan is using ever smaller scopes while still seeing detail on Uranus. In the long thread he used a 12" cat, then an 8" SCT and now a 6" refractor.

I agree with some that a highly processed IR image is not proof of Stan's details. There may not ever be any proof of his claims that will satisfy everyone.

Dave
 

#12 stanislas-jean

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Posted 17 September 2012 - 12:38 AM

You see everybody can have their own opinion, but just opinion.
You see big theories have been raised by imagers with the generation of views with the 685 filter. Now we see others making views with the 742 astronomik the 610 etc.
The 685 may help to get something better with the SNR ratio (to be demonstrated) but what I see visually is the fact that the Uranus contrast levels follow fluctuations, more or less in value and now it seems we are on a good period.
This is the explanation. The planet is not fixed in contrasts, featuring (from an opposition to an other the banding system pattern had changed).
The vision in the R150 is better by the the better scope factor than the mewlon, newtonian and C8 (slightly better).
But this is not prooving this is enough to explain the more easy ability to catch the Uranus pattern except by the fact that contrasts are higher.
So profit of the to_day situation and makes some assessment of the status of to-day.
Stanislas-Jean
 

#13 CPellier

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Posted 17 September 2012 - 03:07 AM

The interest of the 685 is that it's imaging features at an atmospheric level where, mainly thanks to the strong absorption of light of the atmosphere in infrared, they attain a good level of contrast.
SNR is not the problem here as it's much more easy to get a good SNR in visible light, where the planet is much brighter. Also, the resolution of telescopes is much better in visible light.
Respecting to the fact that processing can alter the details, this is possible, as well as other things (like collimation). However if a CCD imager is able to detect details in infrared, he should be skillful enough to get them as well in visible light, where imaging is much more easy due to the amount of light available, and to the better resolving power than in infrared.
 

#14 stanislas-jean

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Posted 17 September 2012 - 03:41 AM

With comparison with the 610 filter which quantified gain the 685 is bringing?
This is interresting to know.
Do we have the idea of which absorption band is involved for the contribution of the image contrast, we have the 619nm (stopped by the 685), the 889nm and after with regards to the chipset sensitivity?
Stanislas-Jean
 

#15 stanislas-jean

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Posted 17 September 2012 - 03:44 AM

Collimation indeed is a strong parameter but I found also the sky transparency and steadiness as well.
Sky transparency.
Stanislas-Jean
 

#16 CPellier

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Posted 17 September 2012 - 04:29 AM

With comparison with the 610 filter which quantified gain the 685 is bringing?
This is interresting to know.
Do we have the idea of which absorption band is involved for the contribution of the image contrast, we have the 619nm (stopped by the 685), the 889nm and after with regards to the chipset sensitivity?
Stanislas-Jean


The RG610 is bringing something like 30-40 % more light, from my last experiences. That's quite a lot. The absorption band is just the broad infrared absorption - from what I have seen this is just like if the CH4 absorption spanned the whole band. After 700 nm we find only narrow peak of emission bands at 750, 820 and 940 but the rest is absorbed.
Here is the spectrum :

Posted Image
 

#17 stanislas-jean

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Posted 17 September 2012 - 06:20 AM

About the cut-off of the chipset,
something around 1050-1100nm?
Are the spectrum compensated with the atmosphere absorption because the absorption bands may be deeper than those shown.
Stanislas-Jean
 

#18 CPellier

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Posted 17 September 2012 - 07:48 AM

Yes 1100 nm.
I don't know, about the spectrum... but I have a better one that I will post tonight.
 

#19 CPellier

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Posted 17 September 2012 - 04:44 PM

Ok so here is the graph I like most, very instructive :)

Posted Image
 

#20 stanislas-jean

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Posted 18 September 2012 - 01:12 AM

Sorry, i cannot catch the graph you intent to insert here at the PC screen.
I give you this link which gives data about albedo values for Uranus.
http://arxiv.org/pdf/astro-ph/9810073"%20/
If we consider the absorption bands in cause it may expected some contrast assessments.
Now this should be combined with the respective sensitivity of the eye and the chipset for a certain evaluation approach.
These graphs were published at the time of the support observations and taking into account the relative variability of the planet pattern the assessment will follow these variations.
Stanislas-Jean
 

#21 Ira

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Posted 18 September 2012 - 05:42 PM

What magnification was being used in the visual observations?

/Ira
 

#22 stanislas-jean

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Posted 19 September 2012 - 12:31 AM

It's mentionned on the sketch issued on the japanese alpo, 333x. That's make 20min arc at the eyepiece.
Stanislas-Jean
 

#23 David Knisely

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Posted 19 September 2012 - 02:03 AM

Tonight (September 19th, 2012 at about 0500 UT), in my 14 inch Newtonian, I used 384x and 596x under fairly decent seeing (diffraction patterns on nearby stars were sometimes fully visible). I saw no detail on the disk of Uranus other than the ever-present limb darkening, which is pretty much what I have seen with the planet each of the times I have viewed it this year. Clear skies to you.
 

#24 stanislas-jean

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Posted 19 September 2012 - 04:24 AM

More than a long discussion i enclose here some expectations about contrast potentially reachable on the planet.
Spectrum are not only for the beauty of the curves but can be exploited for assessments.
The green plus yellow surface correspond to the combination of the planet spectrum (compensated) and the eye sensitivity for a mesopic vision. The R band absorption concerns 1-2% of the green and yellow surface. The yellow surface is about half this surface that makes the contrast improved by a ratio 2 times better.
The pink surface corresponds to the combination of the planet spectum and the 618 chipset sensitivity and the use of the 685 filter. It appears that DR and near NIR bands are involved. The contrast level involved can be 3-5 times better than the level got by visual.
All these levels must have to be pondered by the scope factor and the seing level which reduce them.
More than feelings this help to understand more the capability in each kind of observation.
The 610 filter will involve more seeing perturbation and this could be a fact for going to the 685. This is more the bad influence of the seeing that make poor results rather than the filter selection itself.
Now for visual observation the matter is sufficiently quantified.
Stanislas-Jean

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#25 stanislas-jean

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Posted 20 September 2012 - 12:52 PM

For those who are doubting a lot
http://www.astrosurf...TML/035769.html
sorry this is in french but the photo are RGB and R channel.
Not amazing to catch with 150 and 203mm visually.
Please refer to the above curves annd assessments also this is cross checked.
Thanks Edggie to had maintained this forum open.
Stanislas-Jean
 






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