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#1 penguinx64

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Posted 18 July 2014 - 06:04 PM

How much magnification do I need? 100x? 200x? Or what?
:noway:

#2 CarlosEH

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Posted 18 July 2014 - 07:08 PM

Paul,

Uranus presents a disk in either of your instruments (60mm refractor or 4.5 inch reflector) at a low to medium magnification (40-80x). A higher magnification (100-230x) will present a larger pale blue-green disk that typically does not exhibit much detail. If you are fortunate you may detect delicate detail when the seeing steadies (e.g. faint bands across the disk or over the poles). It is exciting all the same to observe the seventh planet discovered by the great English astronomer Sir William Herschel in 1781 using an excellent but modest 6 inch (15 cm) reflector.

I have attached an observation of Uranus that I made on October 24, 2012 using 7.1 inch Maksutov-Cassegrain reflector.

Regards,
Carlos

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#3 payner

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Posted 18 July 2014 - 07:58 PM

Absolutely stunning drawing and detail in Uranus, Carlos.

Best,
Randy

#4 azure1961p

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Posted 18 July 2014 - 10:55 PM

I never was ae to discern a disc of Uranus with my 70mm at 40x-80x. In my 8", easily. The trouble with the 70mm from my experiences was the comparison stars airy discs at low power were too close in size to make Uranus stand out disk like at all and so very high power of 200x was needed. I think had I a comparison star within very close proximity of Uranus the task would have been far easier but the closest star of similar mag was a star hop process so higher power to exagerratecdiffraction pattern versus angular res was needed. My experiences anyway. I kno of others who've managed with lesser than I in small scopes so...

Nice work Carlos!

Pete

#5 Rick Woods

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Posted 19 July 2014 - 01:21 AM

I believe a lot depends on the quality of the observer. Carlos can discern details that I or other mortal observers could never make out. Carlos gives me a target to shoot for.

#6 David Knisely

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Posted 19 July 2014 - 01:55 AM

This is what I see in my 14 inch Newtonian (and offers a somewhat more realistic idea of how Uranus actually appears in the telescope than some drawings might indicate):

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#7 CarlosEH

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Posted 19 July 2014 - 11:52 PM

Thank you all for the kind compliments on my Uranus observation. I must point out that the albedo features, if present, are typically of low contrast and seeing conditions, collimation, cooling off of the optics, and aperture all play a role. The majority of observations of Uranus will show a homogeneous pale teal disk without significant detail across it.

David - That is an excellent image of Uranus and it's satellites (Ariel, Oberon, and Titania). Thank you for sharing it with us all.

Regards,
Carlos

#8 stanislas-jean

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Posted 20 July 2014 - 04:54 AM

Yes agree for highlighting the difficulty to capture so low contrasted albedo features.
Observers should pay attention to disk light glare that mask the perception. The optimum conditions are on a narrow window, not enough magnification implies glaring, to much washing contrasts.
Reason why the best optical stehl are requested (more than the diffraction limited level) and smooth surfaces.
0.55mm exit pupill diameter is fine for me and sky transparency high.
Stanislas-Jean

#9 penguinx64

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Posted 21 July 2014 - 01:39 PM

Ok, thanks. I don't expect to see much detail. I'll give 100-150x magnification a try for starters. With Mars, that's usually enough to tell it's a planet and not a star. I checked Stellarium and Uranus is about half the angular size of Mars. Maybe I'll have to go as high as 165-225x to see it? That's about the limit for my scope.

#10 Rick Woods

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Posted 21 July 2014 - 03:38 PM

This is what I see in my 14 inch Newtonian (and offers a somewhat more realistic idea of how Uranus actually appears in the telescope than some drawings might indicate):


That's pretty much all I can ever see. But that's why I made the earlier comment; there are observers and observers. I'm a very pedestrian observer. I believe you can be much, much better than I am, and still see no detail on a target like Uranus; but the first-rate observer with the right equipment, environment, and visual acuity can far exceed most of us. In music, these people would be prodigies.

#11 azure1961p

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Posted 21 July 2014 - 07:09 PM

Ok, thanks. I don't expect to see much detail. I'll give 100-150x magnification a try for starters. With Mars, that's usually enough to tell it's a planet and not a star. I checked Stellarium and Uranus is about half the angular size of Mars. Maybe I'll have to go as high as 165-225x to see it? That's about the limit for my scope.


Uranus will be easier than Neptune but both ought to appear as peculiar looking *fat stars* . The use if 226x if you can do it with blessing from the seeing will serve you best.

Good luck and report!

Pete

#12 Rick Woods

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Posted 22 July 2014 - 04:08 PM

That's the point I was trying to make, David. Some observers are gifted, and others are merely skilled.

#13 Bomber Bob

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Posted 22 July 2014 - 07:38 PM

My best observations of Uranus were made about 25 years ago with a 5" D&G refractor at 300x. At that time, I did not see banding; but, I did detect very subtle albedo variations, rather than a uniform pale disk. I didn't have "floaters" in my eyes back then, so I can accept the validity Carlos' sketch made with a larger instrument. In my 45 years of planetary observing, I've found that an experienced amateur with a great telescope and seeing conditions can well exceed the expectations in the guide books or other authoritative sources.

#14 stanislas-jean

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Posted 23 July 2014 - 01:17 AM

Sorry Norme but your views stay on generalities only as also lot of people.
Sorry also to affirm that it is possible to apraise situations.
Seeing effects: studies through analysis of distanced target of very low light, very contrasted features.
Own eyes capabilities: analysis through test Lab Under actual conditions.
Contrast levels on the planet: analysis of expected contrast in different color channels by Spectrum of the planet, we have other means possible.
This is more than generalities.
This is helping to see where the problem is located against an observer ability.
So go ahead and deeper in views.
Regarding ccd we are always placed Under conjectures, explanations, opinions, etc,... the coincidence of data doesnot constitute a proove, they must go also deeper.
Dangerous slide for them.
Stanislas-Jean

#15 stanislas-jean

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Posted 23 July 2014 - 02:09 AM

Here is a set of photo from HST, recent.
If the R channel is centered on 631nm, the more precise methane ray on concern for visual obs is 619nm.
Pushing the contrast at the Sony screen banding is obvious still at R channel here.
Stanislas-Jean

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#16 David Gray

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Posted 23 July 2014 - 10:12 AM

I am sorry you feel insulted as that was not my intent, but as to Stratoscope II.....

http://www.unmanneds....php/t5002.html

A New Analysis of the Stratoscope II Images of Uranus

If it could pick up the rings but no significant disk detail, again, that hardly dismisses anything concerning the Stratoscope II results. Clear skies to you.


OK David not insulted only some concern with being tarred by the same brush in the main.

There is always going to be a degree of ‘artistic’ licence – for myself I strive to ever minimize suchlike – some I guess fall short, or worse, don’t see the point – or wont!! I guess that is because some might consider the planet too trivial (detail-wise) for it to matter – on the contrary they should be even more meticulous if they seriously want credibility – otherwise they risk it reflecting on all of us who are doing our best. That is at the root of my irritations!

With respect as a long-time student of the planet I am well acquainted with such as the processing of the Stratoscope II images. In fact shortly after they appeared an observer put a letter in the BAAJ (Journal) wondering if he had interpreted the ring shadow as a belt on his drawings; and may have done so myself (1969); or belt/shadow combo – see attached (10” Newtonian).

My gripe was with the dismissives (the ‘proof’) aimed at visual by those using the original (unprocessed) images. As for the processed: I see nothing to seriously conflict with the level of contrasts I was perceiving/recording back then – or since for that matter.

My drawings from then are with the BAA Saturn Section now (Uranus/Neptune a sub-group). Also in a couple of Journal reports/papers by the late Andy Hollis director of the then Asteroids and Remote Planets Section. What I show here is from a compilation requested by Paul Abel a few years back. These are ‘rescans’ (digital camera shots).

Part of my brief has been to interpret/reconcile historical observations with what I see: especially of late as the planet becomes ever more favourably placed here.

I need to cut short here as we are currently on limited broadband – transitioning to a new/better ISP/Phone setup this day hopefully.

Hopefully by I return, if the thread is not locked, :grin: I may elaborate on what I say here. For an object that offers so little it certainly engenders a lot of verbosity!

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#17 David Gray

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Posted 24 July 2014 - 06:05 AM

So far so good with the new Internet (ISP) – already better than the old: and we were told to expect sluggishness for a couple of weeks………!

I was pleased to see Stan’s Hubble attachment as it can be used to illustrate a vexing point about individual monitor settings.

If there are those who can’t get banding on the visible-range images I suggest adjusting their settings slightly to see if they can then. Or even viewing the screen with dark glasses or such.

I have pasted Stan’s into Corel and done very minimal adjusting – see attachment.

What I am trying to say is it is not enough to see these images on our respective monitors and pronounce that the presented contrasts portrays exactitude.

That is the problem: a while back we had a family get-together with my two desk-top PCs and 4 laptops. As an experiment we all viewed various drawings etc with all of them set on default-display. All were markedly different – on two of the laptops some of my drawings looked grossly misrepresented as regards contrast – almost lost the will to post stuff anywhere! At the same time photos/images were more equable ……!!

The monitor I have done the attachment on my main workhorse-PC it is possible to very finely calibrate. The newer PC display has dumbed-down setting facilities (difficult to finely calibrate). I addition there is a marked vertical-brightness gradient - tho’ the horizontal viewing angle is excellent. Thing is when I viewed Stan’s attachment near the darker top area of the newer-PC screen the banding was very distinct even on the weakest image – even to my wife’s failing eyes. But the impressions I report here are relating to what my well calibrated monitor shows.

Dave.

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#18 stanislas-jean

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Posted 24 July 2014 - 09:16 AM

Personally I did this on the 29th september 2012:
http://alpo-j.asahik...12/u120929z.htm
not bad.
Stanislas-Jean

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#19 Bomber Bob

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Posted 24 July 2014 - 09:53 AM

Stan, your third sketch is very similar to what I recall seeing years ago. I'm sure everyone has their own techniques for confirming minute / subtle details; what I do is move the object to other points in the FOV, in case it's a distortion in the optic path; I'll also look away for a bit, and then see if it persists, before sketching it. I also intentionally refrain from checking ephemerides & maps before I observe the planets to avoid biasing my observations.

#20 stanislas-jean

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Posted 24 July 2014 - 12:54 PM

The one of the main things is to be sure of the orientation of the image in the eyepiece.
This is not the start of the observation, but after capturing something, try to make connection with the orientation of the image, but not vice versa.
Don't push the time at the eyepiece say more than 20-30s otherwise imagination force you to see. You have to fight against this. With some times at the eyepiece you can succeed in that way and acquire some selfcontrol.
Note what you see, change subject to observe 5-10 minuts and come back. Leave the previous observations without consulting the notes and try again, then after 2 or 3 more trials, compare. If this is convergent you can publish and compare with others, HST, etc...
One question: how do you see the planet color?
Personally at 1mm exit pupill diameter this is more yellowish than bluish and statistically, people who reported were on the same, I noted with them during tests. Features are more located visually on the red channel, 619nm.
Not a matter of years old but sensitivity a little shifted under mesopic conditions.
Mesopic conditions and against abilities involve different responses from a guy to an other.
That's nature and Gift as a potential given, not matter of ego.
I feel that ccd can do better than us but until exposure times will be 0.25-0.50s and chipset color responses, they will handicaped.
As they do not intent to perform test for simulating actual conditions to show their physical limits, artifacts will be their must, dayly.
For Neptune, situation is worst.
I am just forcing on blue berries on breakfast mornings with Talieh, my wife. This helps a lot for sure.
Stanislas-Jean

#21 Bomber Bob

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Posted 24 July 2014 - 04:41 PM

At low power, Uranus is a very pale blue to me. At high power, it's washed-out and colorless.

#22 David Knisely

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Posted 24 July 2014 - 09:16 PM

At low power, Uranus is a very pale blue to me. At high power, it's washed-out and colorless.


In my 14 inch, it is an almost sky blue to me as well, like the color of a clear crisp daytime sky not quite overhead but the bluish of the sky somewhat closer to the horizon. At powers over 400x, the color starts to fade somewhat but it still shows at least a hint of a pale bluish hue with notable limb darkening (but little else). It has never shown any other coloration. Clear skies to you.

#23 azure1961p

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Posted 24 July 2014 - 09:51 PM

When I was a kid, 13(?) I saw the aqua color people often report - at the time i didnt even know what i was seeing in terms of what planet by name (oh youth). These days - through adulthood - even with twice the aperture - its this slate warm grey . The app Sky Safari has it nailed perfectly for me, albeit, far brighter and bigger.

These outter two minimalist planets convey the sense of enormity our solar system is in ways I can't feel any other way.

Pete

#24 stanislas-jean

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Posted 25 July 2014 - 12:47 AM

Mesopic vision is special, being the combination of the basic modes, photopic and scotopic. From a guy to an other the mesopic spectral response is different with enhancement of the reddish part more or less.
There is no other explanation.
Stanislas-Jean.

#25 David Gray

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Posted 25 July 2014 - 03:58 AM

There seems to be something with the Uranian wavelengths that confounds many as regard it’s perceived hue.

I tend to the impression that it is particularly sensitive to whatever I was looking at previously. Whilst I would say overall I get a pale cyan. I have in my notes over the years such as: “struck how yellow the planet looks tonight”. Sometimes a creamy green, and it tended more toward green when it was for many years a low altitude from here. A purer Cyan to me these recent years.

I suspect it is particularly sensitive, at least in my case, to whatever light source had been viewed just prior. During those 1969 observations some nights I got it greenish others in equal conditions a strong sky blue. Back then I used a red light for drawing etc and always wondered if that pushed me to seeing it green; I have no recollection if with those sky blue episodes I had the light on – I only drew it when I believed I was getting detail so light on – in fact I associated no detail with sky blue as I have noted retrospectively in my BAA reports when interest in the planet became ‘respectable’ – early 90s under Andy Hollis. Previously I kept them in a shoe box under the bed never really thinking anyone would be interested; as you mentioned very guardedly that you were actually getting detail or even looking for it!

Untested scientifically but I seem to have extended vision at the red end and perhaps might give me an edge with Uranus – and might account for the fact I find a red observing light uncomfortable at any level – what others find right I find very glary. Arcturus always looks much brighter than Vega to me when they can be compared in equable conditions.

I find Neptune consistently strongly blue even, as recently, with x610 (binovu) and always simple to pick out due to this in my 3” x55 which is second finder on the 16.3” D-K.

I was given some observations by Peter J. Young (deceased/died in tragic circumstances). He was studying under de Vaucouleurs at one time, whom he had impressed very much. In 1974 Peter used a 9”refractor, a 36” reflector and the 84” at Kitt Peak; in the latter he found Neptune very blue but he described Uranus as “Creamy-grey” Also he drew belts/zones and a distinct polar cap!

Peter often observed deep into the night and consequently fell asleep during lectures and reportedly avoided being ejected only because of de V’s great regard for his abilities! He was an accomplished planetary draughtsman – some of his work is in the BAA Jupiter Memoirs.

DG






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