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Uranus in Twilight and Through Cloud!

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#26 David Gray

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Posted 25 July 2013 - 07:20 AM

I do not believe that privately sharing that material for research purposes would be an infringement of copyright.


A shame that anyone’s dedicated work might be denied us for more general inspection/appraisal.

These days we have a ready tool to give an extra check on older observations in the form of WinJUPOS. Alluding to Roth’s “Handbook for Planet Observers” (1970) on Plate 29 are eight drawings captioned “Drawings of observations of Uranus with 4-inch and 10-inch instruments in the years 1936 (top left) and 1949 (bottom right)”

Unfortunately not very forthcoming on dates/times etc. But for the years given both drawings suggest an equatorial aspect particularly 1949 which in fact WinJUPOS shows to be very polar and 1936 well advanced toward polar! In contrast with Schiaparelli’s 1880s observations for which WinJUPOS shows Uranus to be more equatorial in presentation.

So with WinJUPOS we have a convenient way to more qualitatively/fairly evaluate past observations. At least better than draw some arbitrary line based on some observational failure/’success’ (illusion-wise) to see features without full appraisal of the methods used- i.e. such as disregard of the proper light-level so more risking any diaphanous features are lost or the manifestation of spuriosity. Of course it is vital to show the field-orientation with drawings/images; many fall short with this sadly.

I could add a host of pitfalls; and as I have said several times before: “this planet is not for the faint-hearted nor the reckless”. I try to adopt a relaxed benignly objective approach at the eyepiece – as opposed to gullible/wishful-thinking and certainly not the respective angsts of failure-fear or cynical-negativity!

Cheers,
Dave.

#27 krakatoa1883

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Posted 25 July 2013 - 08:03 AM

p.s. I do not believe that privately sharing that material for research purposes would be an infringement of copyright.


Agreed, let me collect the drawings, there should be no problem in sharing them with you and Dave. However it would be even better to write something on Schiaparelli's observations of Uranus, for the JBAA for example, as far as I know there is almost nothing in the literature on this subject.

I think 8 inch aperture be totally inadequate for the routine study of the planet, although there have been reports of unusually conspicuous details seen with small instruments. As Venus, Uranus can be particularly prone to produce illusory details.

#28 stanislas-jean

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Posted 25 July 2013 - 09:48 AM

Keep in mind Raf that Mr O'Meara fixed the Uranus planet rotation with spots help with the use of a 232mm refractor only.
This depends on the observer own acuity mainly and relatively less by the aperture in presence. Apertures will not grow contrasts above the actual contrasts of the planet itself, they are weak already and not obligatory illusion results.
Stanislas-Jean

#29 idp

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Posted 25 July 2013 - 10:25 AM

Keep in mind Raf that Mr O'Meara fixed the Uranus planet rotation with spots help with the use of a 232mm refractor only.
This depends on the observer own acuity mainly and relatively less by the aperture in presence.


I disagree. O'Meara's observations depended on the appearance of highly unusual features in Uranus's atmosphere (kind of, a GWS on Saturn). If memory does not fail me, the same observer could not see anything on Uranus during the previous 20 years.

Ivano

#30 stanislas-jean

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Posted 25 July 2013 - 12:45 PM

Spots I wrote about, please re-read.
Stanislas-Jean

#31 idp

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Posted 25 July 2013 - 02:08 PM

OK, re-read. What's wrong with what I wrote?

I did not mean that he saw the physical equivalent on Uranus of a GWS, but that it was an unusual phenomenon; not something you can regularly watch on Uranus every night with a 9-inch instrument - regardless of how awesome your eyesight is. Hence my comparison to Saturn's GWSs.

Ivano

#32 azure1961p

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Posted 25 July 2013 - 04:24 PM

Hi Ivano,

I think it was the twenty years following not preceding that famous observation for Omeara that he saw nothing like it again, as he was a college student at the time. I'm going off memory here too. He DID address the caution of imagining details just a few years ago in one of his ASTRONOMY mag. columns as it seems to have reached his desk some rather regular reports of details were occurring and so he stressed the need to be careful when interpreting such things.

Pete

#33 idp

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Posted 25 July 2013 - 05:18 PM

Yes, I saw the drawings and read the papers but I cannot check right now, so I may well have misremembered. My point was that it was an unusually visible event on Uranus that allowed him to work out a rotation period, rather than his own visual acuity. I think the point still stands.

Ivano

#34 azure1961p

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Posted 25 July 2013 - 07:33 PM

I totally agree . What'a more O'Meara had a fellow observer witness the unusual feature where they agreed it resembled a planetary nebula with a doublestar at its center. . No slight to O'Meara who I admire but it would seem it would've been visible to the average careful attentive observer with such an instrument.



Pete

#35 John Boudreau

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Posted 25 July 2013 - 09:13 PM

I totally agree . What'a more O'Meara had a fellow observer witness the unusual feature where they agreed it resembled a planetary nebula with a doublestar at its center. . No slight to O'Meara who I admire but it would seem it would've been visible to the average careful attentive observer with such an instrument.



Pete


The 2nd observer was Peter Collins who worked at the observatory at the time, and is currently on the staff at Lowell Observatory. There was at least one or two others that saw the spots too.

We were all members of the ATM's of Boston at the time, and I did some very limited observing after monthly club meetings with them and a few other members when conditions allowed. They were at the 9" Clark nearly every clear night, and I think O'Meara used to say he was up there every clear night! :grin:

However, I had never seen Uranus in the 9" Clark until September of last year. The spots had been seen in August--- can't recall the year but I think it was in the early '80s. The club didn't have meetings from June to August, so I wasn't around at the time of the observations.

#36 stanislas-jean

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Posted 26 July 2013 - 12:55 AM

About spots on Uranus, the performance of Mr O'Meara is a performance.
Why?
Because at that time we didn't have the Keck for providing us the presence of the recent spot. It is easy to-day to see more something as the event was already revealed.
As other examples encke division, saturn pole hexagonal, etc....
Otherwise the probability to catch them are say low.
The last recent spot on Uranus revealed by the Keck was seen personally from two different times and nights as a weak milky stain that seems to float above.
This is extremly difficult to catch at the 12".
Having done a biblio research on the subject, in past (recent) was captured by big guns spots like with different contrasts level from 0.5 until 40% (extremly rare).
Uranus is well observed, as it seems, and the publications about rare and access difficult.
On amateur activity, the observations are only few and I think this merits more time survey.
The example of Mr O'Meara is interresting also by his personnal investigation in times for the follow-up and with average aperture.
He wins his challenge, in the 80ies, with less knowledge about (scope factor, acuity quantification, planet knowledge, etc) and surely highly motivated.
Banding was not on the reports but spoting was, that does already an excellent performance.
Stanislas-Jean

#37 stanislas-jean

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Posted 26 July 2013 - 01:09 AM

"OK, re-read. What's wrong with what I wrote?

I did not mean that he saw the physical equivalent on Uranus of a GWS, but that it was an unusual phenomenon; not something you can regularly watch on Uranus every night with a 9-inch instrument - regardless of how awesome your eyesight is. Hence my comparison to Saturn's GWSs. "
The comparison with Saturn is harsch to do.
I think Idon't know if the dynamic of events on Uranus is similar to Saturn (spotting with panache behind).
The contrasts are not the same as you know.
On an opposition you can invest lot of nights on the subject, 40-50 nights per since 2 opposition personnally.
But frankly the subject is not the same as the other planets, this requests some acclimatation on and some training, Venus being a 1st step for maintening the training.
And somebody says here look on the planet not at.
9" is a good aperture with a good acuity.
Uranus is also from my opinion changing and contrast levels also fluctuating (biblio research reports this also).
Stanislas-Jean

#38 krakatoa1883

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Posted 26 July 2013 - 11:17 AM

O'Meara's observations depended on the appearance of highly unusual features in Uranus's atmosphere (kind of, a GWS on Saturn)

Yes, Ivano, they were unusually bright spots. The full story is narrated by Thomas Dobbins in September 2012 issue of Sky&Telescope, pp. 54 - 56. The author writes "For months O'Meara saw only the limb darkening of a disappointingly bland globe through the Harvard College Observatory's venerable 9-inch Clark refractor, until two brilliant spots suddenly appeared etc."

As you know the book "The planet Uranus", by Alexander, is a must reading for the history of observations before the space age.

#39 ericj

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Posted 04 August 2013 - 08:22 PM

Hi David,

Very interesting topic thanks for posting it.

Best,

Eric

#40 David Gray

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Posted 09 August 2013 - 07:29 AM

Thanks Eric,

Been all over the place lately - I have some reasonable Uranus (& Neptune) obs. in hand but they will keep for now!

David.

#41 stanislas-jean

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Posted 12 August 2013 - 02:52 AM

Here are the observations performed last 11th with a MC180mm on Uranus.
Conditions were optimum with regards to the conditions (S:6-7/10 15° above horizon only).
Observations were stopped by the clouds coverage in sky at last.
South at right down side. North hemisphere dark is the more conspiscious feature. EZ was not appearing appart a slight continuous brightning. South hemisphere was dark light and seemed to be bordered by a darker albedo edge, the cap being clearer (the clearer feature).
Images on stars at the zenith were quite fixed (S:10/10 with 450x). Was an excellent night and the atmosphere exceptionnally steady.
3 satelites were seen by moments to long ones.
The 305mm is not yet installed the season was very hot until these days, we will see later for a step more in readability features. The MC180 is presently here more acurate than the µlon180 and the C8 used last opposition.
Stanislas-Jean

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