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Ira
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Reged: 08/22/10

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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5428041 - 09/18/12 06:42 PM

What magnification was being used in the visual observations?

/Ira


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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: Ira]
      #5428614 - 09/19/12 01:31 AM

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


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David Knisely
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Re: Uranus cloud bands in a C8 new [Re: Ira]
      #5428678 - 09/19/12 03:03 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.

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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: David Knisely]
      #5428727 - 09/19/12 05:24 AM Attachment (64 downloads)

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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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5431000 - 09/20/12 01:52 PM

For those who are doubting a lot
http://www.astrosurf.com/ubb/Forum3/HTML/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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CPellier
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Reged: 08/07/10

Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5431335 - 09/20/12 05:06 PM

Quote:

For those who are doubting a lot




Ok, but I have better images with the same diameter that do not show the belt in R (maybe with the RG610)



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azure1961p
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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5431518 - 09/20/12 07:09 PM

[/qoute]Not amazing to catch with 150 and 203mm visually.




Well if that's not amazing then it'd be amazing for a four inch refractor? Or my 70mm?

Stan what was the aperture of the scope in those Uranus pics at astrosurf? They are interesting.

Pete

Edited by azure1961p (09/20/12 09:26 PM)


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azure1961p
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Re: Uranus cloud bands in a C8 new [Re: azure1961p]
      #5431522 - 09/20/12 07:13 PM

Mr. Pellier,

The R610 does indeed appear to show atleast a thread of a lighter colored zone by the pole. The other is a little too ambiguous .

Pete


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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: azure1961p]
      #5432044 - 09/21/12 01:38 AM

250mm Pete.
It's not amazing as the contrast on the period get a better level.
Christophe it's time to change, not for me but for all the prvious past great observers (Fournier, Antoniadi, de Vaucouleurs, here O'Meara...).
For imaging we had J Sussenbach who succeed too but not as clear than Fisac, we have others (russians among them).
At present there is D.Peach who performed the best Uranus image with his 355mm but in near NIR, clearer than the 1m.
It last.
Stanislas-Jean


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CPellier
scholastic sledgehammer


Reged: 08/07/10

Re: Uranus cloud bands in a C8 new [Re: azure1961p]
      #5432116 - 09/21/12 04:22 AM

Quote:

The R610 does indeed appear to show atleast a thread of a lighter colored zone by the pole. The other is a little too ambiguous .




Hi Pete, yes I agree with you.

Quote:

Christophe it's time to change




If I get certain that there is something to see in R, I will say it - and I will get it on images.

Quote:

For imaging we had J Sussenbach who succeed too but not as clear than Fisac, we have others (russians among them).
At present there is D.Peach who performed the best Uranus image with his 355mm but in near NIR, clearer than the 1m.




Among these shots you have IR images - not visible R. Only details in IR are recognized. On images galleries you have also many noisy images that carry false details. You would have to learn to recognize them, especially on Uranus images don't believe everything you see - or only what you want to see... My R above is better than any that will find elswhere.


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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: CPellier]
      #5432174 - 09/21/12 06:13 AM

Yes it last.
Stanislas-Jean


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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5447943 - 09/30/12 05:18 AM Attachment (63 downloads)

My last observations got with now the 305mm.
Yesterday evening the images were average to good for a short time (just before the moisture deposition on the vegetation).
Here are the results, not bad for the least as after a 35-40 minuts time the features appearing at the morning limb became more present and those at the evening limb side fade. The dark collar that was present one month ago is not now.
The 2 bands bordering the equatorial zone are the the darkest ones with albedo variation all along to the longitude.
A brightening at the equatorial zone morning side was appearing as shown. There is no planet phase angle at present.
This needs indeed more data for the confirmation and suggest to anybody following this planet to capture data at intervals, each hour for instance in order to show featuring rotating with the planet.
Survey is to be continued.
Stanislas-Jean


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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5454474 - 10/04/12 01:44 AM

Some interresting data here, recent.
Good read.
Stanislas-Jean
http://alpo-j.asahikawa-med.ac.jp/kk12/u120915z.htm
http://alpo-j.asahikawa-med.ac.jp/kk12/u121001z.htm


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David Knisely
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Re: Uranus cloud bands in a C8 new [Re: stanislas-jean]
      #5454529 - 10/04/12 02:52 AM

I observed Uranus on September 20th, 2012 at around 0500 UT in my 14 inch (355.6mm) aperture f/4.6 Newtonian at from 384x to 596x. I saw nothing on the planet's disk other than limb darkening despite some pretty good seeing (that night, I was able to use up to 961x on the small planetary NGC 6891 in Delphinus to show the object's tiny inner ring and central star). Clear skies to you.

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stanislas-jean
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Re: Uranus cloud bands in a C8 new [Re: David Knisely]
      #5454638 - 10/04/12 07:35 AM

I am sorry.
Stanislas-Jean


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stanislas-jean
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Re: Uranus cloud bands in a C8 [Re: stanislas-jean]
      #5462386 - 10/09/12 03:47 PM

Interresting link
http://alpo-j.asahikawa-med.ac.jp/kk12/u121005z.htm
nevertheless that needs more confirmation.
It seems the bands are not purely circular.
To be followed narrowly.
Stanislas-Jean


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azure1961p
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Re: Uranus cloud bands in a C8 [Re: stanislas-jean]
      #5463182 - 10/10/12 12:40 AM

Looks like processing artifacts - or rather, over processing. I believe the belts imaged are real but the irregularities are artifacts. I will be following this thinly.

Pete


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stanislas-jean
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Re: Uranus cloud bands in a C8 [Re: azure1961p]
      #5463234 - 10/10/12 01:33 AM

Why? because others didn't.
Stanislas-Jean


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John Boudreau
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Re: Uranus cloud bands in a C8 [Re: stanislas-jean]
      #5463274 - 10/10/12 02:32 AM

Quote:

Why? because others didn't.
Stanislas-Jean



Stan, I'm sure you've seen limb diffraction effects on images of other planets. The strongest examples would probably be the bright ring that can result on the sunward limb of Mars or Venus, and many times a secondary bright ring occurs just inboard of the outer limb ring. Along with those bright rings there are alternating dark rings. The intensity of this effect varies with seeing effects and with accuracy of focus, along with the size of the scope's aperture (they are much less of a problem with the PDM 1meter, for instance).

When the same effect shows up with a small angular target like Uranus, the secondary bright ring creates an artifact within a large area of the planet's disk and the secondary dark ring can create a dark zone or ring in the center--- in the worst cases, it can appear to look like a poorly defined Fresnel pattern. Also, with the somewhat longer exposures used for such a faint target like Uranus the effect appears softened. In the case of the image you're referencing, it appears to have caused a ripple distortion in the planet's banding.

The same effect also can be seen many times in images of the Galilean moons as they are so small in angular size. To a lesser extent it also affects Mars when the disk gets down to around 4" or so.


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stanislas-jean
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Re: Uranus cloud bands in a C8 [Re: John Boudreau]
      #5463330 - 10/10/12 05:33 AM

John thanks for your thoughts here.
However, it can be discussed long times about the possibility to get strange results or not.
This is not the debate actually because meaning the fact that for each the method in use is by definition reliable. This is not so easy acquired and demonstrated.
What I note this this the results of the italian observers that raise subtil results, russian as well. Nobody knows what kind of materials they employed (not the scope that is declared, but the environment around the scope).
What i can witness is the fact that albedo variations are present, not only on limbs visually.
What i can bring also, these are reports and publications (issued in public domains now from 2005 and 2007) from Keck teams for Uranus, these comments are about featuring on the disk reported in IR light. This opens the possibility of the collection of albedo variations and for making narrow surveys about without consideration of prior admitted views. It's important to perform as. I am still convinced that against so light contrast variations some "calibration" of the views are to be undertaken. It's matter of reliability and confidence at final.
The visual observation doesnot meet the same kind of problems and can be assessed in parallel ways, the long distanced targets as an example.
Anyway more data and investigated-calibrated methods are needed for a confidence.
Stanislas-Jean


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