128 replies to this topic

[David Gray]

A recent result to demonstrate orientation in particular:

 

I prefer to depict Field Direction (Eyepiece); avoiding the IAU-befuddled N Pole/S Pole ambiguity-risking confusion. 

 

As shown I go for overkill with Uranus (and Neptune) by including a WinJUPOS grid for the date.

 

DG

 

Edit Note: just landed in my Inbox - http://lnk.nu/keckob...atory.org/1ci56

Attached Thumbnails

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Edited by David Gray, 09 August 2014 - 12:18 PM.

[star drop]

one here making comparision between galaxies light level and planet light levels including Uranus: this means he read noting about the evaluation and especially the mesopic mode vision,

Stanislas-Jean

 

It appears that you misunderstood my post. The point of which is that I do not include background stars in my deep sky object sketches because they are always there and often too numerous. This relates to limb darkening. It is always there. I have a sketch of Jupiter (which appears to be lost) when the comet fragments impacted and I did not include limb darkening and only depicted a few of the prominent cloud bands. The impact sites looked like holes with a dark center and a less dark periphery. So I only included details about the new stuff that time.

 

When I view M105 and brighter galaxies on a transparent night their cores range from creamy to yellow tinted, some planetary nebulae show both blue and red regions, the brighter stars in globular clusters are orange and the nebulosity in and about the Pleiades is blue with the outermost region being chocolate gray.

Is that not mesopic vision?

 

Ted

[Illinois]

Interesting posts! Love to read and learn something!  Uranus should be little easier to find this and next year! It getting closer to Zeta star and below Epsilon star in Pisces!

[azure1961p]

Hi Ill,

 

id bet your 7" Mak would give a very sharp disc at 400x.  Incidentally and as an aside to the thread topic - I kno in the past you've mentioned cooling issues with your Mak.  Id really really really consider contacting Lymax for there fan cool attachment. Very simple to use and you'll probably have thermal equilibrium in thirty minutes as opposed to two hours.  Again though, being that this is a high power object to be sure it'd seem to play well in to your maks sweet spot.  In a couple weeks I'm going to start an observing program with my 8" and see what cones of it .  Based on Grays subtle indications its optimistic for me to expect banding but there's always the moons too to chase down.

 

Stellav- thanks for the comments.  I kno the limb shading isn't easy on such a small object at least with my scope but when it pops in its actually the rewarding sight - and then there's the practical points I covered.

 

Nice illustration and tutorial Dave.

 

Pete

[David Gray]

Thanks Pete – was just to show how quick and simple it is to pre-draw the shading.  Observational considerations aside this part of it surely within the abilities of a moderately gifted older child………

 

You made a very valid case for using it as a standard intensity with Uranus – also Neptune!

 

Of course with planetary drawing in general some prefer the more diagrammatic approach.

 

Even so I have several times been approached by despairing would be planet-depicters saying that their drawings always look flat and ‘lifeless’ – the reality missing somehow in spite of them getting a good detailed drawing.  They become discouraged trying to capture that while they are drawing.  The solution I tell them is to add a degree of shading before they apply the main albedo features.  Limbs with the gas giants and terminators with the others as applicable.  Amazing how their confidence grew with this simple indication that they are looking at and drawing a globe rather than a 2D disk.  Even with Saturn which betrays its true ‘3D –ness’ in several ways. 

 

As I have said elsewhere, before drawing at the telescope, from age 11 –16+ I executed hundreds of drawings at the eyepieces of microscopes.  At the start of that I too could not quite grasp why my drawings looked flat and lifeless; until my artistically gifted mother showed me the ‘trick’ of simple shading to get that truer effect.  So quick and simple with stumps – why would we shy from it?  From then on my microscopic subjects were viewed with new eyes and new delights: I started to become an observer – surely transferable to the telescopic………..!!

 

Maybe I should have took some of this to the Sketching Forum; but I argue some observational applicability here in light of some of the forgoing posts. 

 

If anyone calls me an artist of any sort I might be offended     Planetary Draughtsman please   

Dave.

Edited by David Gray, 10 August 2014 - 10:32 AM.

[David Gray]

Assuming some visual detection it might be interesting to see if those spots induce those apparent anomalously inclined ‘belts’ (“Faint Belts Aslant” – Alexander “The Planet Uranus” page 178).

 

Those ‘Y’ markings also might also be similarly induced in the eye by disparate light spot placement it has been conjectured coupled with seeing and

resolution limitations.

 

DG

Edited by David Gray, 10 August 2014 - 12:24 PM.

[Special Ed]

Thanks Michael,

 

"See"?  As in the eyepiece as opposed to imaging?

 

That might trigger some storms on here.....................  

 

July 17 on ALPO-J:  http://alpo-j.asahik...14/u140717z.htm  

 

Dave.

 

Well, That's a good question.  I emailed Phil Plait but when I got back here, Stanislas had already answered it.

 

Your July 17th drawing (I'm reluctant to call it a "sketch"   ) is quite interesting.  I wonder what the longitude of the storm that Keck imaged is?  Then you could compare your observation.

 

Thanks for the info, Stanislas.

[David Gray]

 

Thanks Michael,

 

"See"?  As in the eyepiece as opposed to imaging?

 

That might trigger some storms on here.....................  

 

July 17 on ALPO-J:  http://alpo-j.asahik...14/u140717z.htm  

 

Dave.

 

Well, That's a good question.  I emailed Phil Plait but when I got back here, Stanislas had already answered it.

 

Your July 17th drawing (I'm reluctant to call it a "sketch"   ) is quite interesting.  I wonder what the longitude of the storm that Keck imaged is?  Then you could compare your observation.

 

Thanks for the info, Stanislas.

 

Well that could come later - not wanting to influence myself at this stage and my being entirely ignorant of the specific latitude rotation period is a factor.

 

But if my 'spot/s' have reality this is quite independent as the drawing was sent straight off  .

 

Of course there is WinJupos CMs: but was never sure what rotation they were based on; but at least my uncertainty lessened any influence! 

 

Dave.

Edited by David Gray, 10 August 2014 - 12:48 PM.

[stanislas-jean]

 

 

Thanks Michael,

 

"See"?  As in the eyepiece as opposed to imaging?

 

That might trigger some storms on here.....................  

 

July 17 on ALPO-J:  http://alpo-j.asahik...14/u140717z.htm  

 

Dave.

 

Well, That's a good question.  I emailed Phil Plait but when I got back here, Stanislas had already answered it.

 

Your July 17th drawing (I'm reluctant to call it a "sketch"   ) is quite interesting.  I wonder what the longitude of the storm that Keck imaged is?  Then you could compare your observation.

 

Thanks for the info, Stanislas.

 

Well that could come later - not wanting to influence myself at this stage and my being entirely ignorant of the specific latitude rotation period is a factor.

 

But if my 'spot/s' have reality this is quite independent as the drawing was sent straight off  .

 

Of course there is WinJupos CMs: but was never sure what rotation they were based on; but at least my uncertainty lessened any influence! 

 

Dave.

 

I had a look this morning on Uranus with using the 203mm Cassegrain.

Full moon a little disturbing as the sky was hazzy and windy conditions. Average conditions with 3-4/10 images (poor) with periods of 5-6/10 images at 333-350 and 400x.

Banding structure was appearing faintly with something not clear near the CM at around 02H10UT (below the equator circle), nothing noted at the limbs.

Observations ware leaded between 01H30 to 03H00UT (CM 178-193°).

South hemisphere (according to HST orientation) was the darker feature, north hemisphere was clearer grey tone with a darker part at the north band limit, north pole (according to HST orientation) was clear.

The report will be accessible this week on the japanese Alpo site.

The patch collected near the CM (may be at CM 150° around) is uncertain with regards the sky conditions, the present seeing and the aperture in use, was not enough seen.

If the patch collected is the features object to the alert, this is not well contrasted even using the W8 filter.

I will try again with a bigger size, hope the sky will be steadier.

(For the information, the limb shading is an help for finding the right focusing point, when appearing very clear you are. Easily confirmed when watching after stars which exhibit a clear diffraction pattern).

CM were calculated with winJupos.

Stanislas-Jean

[Special Ed]

Stanislas,

 

This interesting pic was posted over in the imaging forum by an imager in Russia under very good conditions.

[stanislas-jean]

Stanislas,

 

This interesting pic was posted over in the imaging forum by an imager in Russia under very good conditions.

The observer, Alexander, is known on the japanese Alpo. He performed already good to excellent data on Uranus.

And presently.

I have to push in aperture here.

Stanislas-Jean

[azure1961p]

On balance though (Mr. Penguinx?) the pole side while not revealing banding of course did manage to burp up some disturbances that Stephen James Omeara AND a witness were privy to in which these two bright spots about the pole very much echoed a planetary nebula with a double central star! Of course he was at it for quite a while and the pole as the flyby reveals was poker faced bland. At anyrate, Omearas observations were so exacting he came within a very close number on this planets actual rotation period.

 

My feelings on the pole end view are then that the flyby empty picture was merely a snapshot of what can be a very dynamic place - but in its own time - which might prove to be substantial based at least on the nights SJO saw but a blank disc.

 

Pete

Edited by azure1961p, 13 August 2014 - 07:48 PM.

[John Boudreau]

On balance though (Mr. Penguinx?) the pole side while not revealing banding of course did manage to burp up some disturbances that Stephen James Omeara AND a witness were privy to in which these two bright spots about the pole very much echoed a planetary nebula with a double central star! Of course he was at it for quite a while and the pole as the flyby reveals was poker faced bland. At anyrate, Omearas observations were so exacting he came within a very close number on this planets actual rotation period.

 

My feelings on the pole end view are then that the flyby empty picture was merely a snapshot of what can be a very dynamic place - but in its own time - which might prove to be substantial based at least on the nights SJO saw but a blank disc.

 

Pete

 

There were two witnesses to O'Meara's observations and timing of the bright spots. One was Peter Collins, who at that time was working at Harvard Observatory--- IIR, he discovered at least 3 nova visually, including Nova Cygni 1992. Collins is currently on the staff at Lowell observatory. The other was comet hunter Michael Rudenko, who now currently works at the IAU's Minor Planet Center. Along with O'Meara, these individuals were/are highly skilled observers.

[stanislas-jean]

 

On balance though (Mr. Penguinx?) the pole side while not revealing banding of course did manage to burp up some disturbances that Stephen James Omeara AND a witness were privy to in which these two bright spots about the pole very much echoed a planetary nebula with a double central star! Of course he was at it for quite a while and the pole as the flyby reveals was poker faced bland. At anyrate, Omearas observations were so exacting he came within a very close number on this planets actual rotation period.

 

My feelings on the pole end view are then that the flyby empty picture was merely a snapshot of what can be a very dynamic place - but in its own time - which might prove to be substantial based at least on the nights SJO saw but a blank disc.

 

Pete

 

There were two witnesses to O'Meara's observations and timing of the bright spots. One was Peter Collins, who at that time was working at Harvard Observatory--- IIR, he discovered at least 3 nova visually, including Nova Cygni 1992. Collins is currently on the staff at Lowell observatory. The other was comet hunter Michael Rudenko, who now currently works at the IAU's Minor Planet Center. Along with O'Meara, these individuals were/are highly skilled observers.

 

This is not sure also that the aim of voyager was to take pictures high resolution of the planet and according the means in game.

According the data I had from the Harvard public Library, the red filter used for Imaging was centered on 0.635µm and was bandpass width filter occulting the 0.619µm and above the 0.700µm of the methane rays. This can be an explanation.

The second explanations being the fact that on the surface the contrast being low (expected to be around 2% and less (around 5% in NIR) was not targeted with their camera.

I donot know which camera they used actually because given in the publications (surely not a QHY5L or ASi 120 or 618 or similar).

I donot think this is an adaquate reference with the image provided.

Now publications about the fly by reported an activity on the planet on the time of the observation period.

I gave the references in the past year forums on the subject.

 

I think also the named observers were full experienced and what were reported was consitent and pertinent.

Defining rotation period of the planet from features well seen is a proove that is confirmed now with the most data collected lastly, since years. This is enough for.

More merits for works performed in unknown fields with no references (HST, Keck, etc...) at the time of performance.

Stanislas-Jean

[Love Cowboy]

I thought I read it theorized once that the blandness of the disc at the time of Voyager had something to do with the orientation of Uranus at the time; and by that I mean, not just the orientation toward the camera, but the orientation toward the sun.

 

Uranus' extreme axial tilt probably has an effect on the seasons far more extreme than that of any other planet.  When it is summer in one of Uranus' hemispheres, that is when one of the poles is pointed toward the sun, the area of the planet experiencing "midnight sun" conditions like the Arctic Circle here on earth would encompass most of that hemisphere; and likewise most of the other hemisphere remaining in darkness throughout the rotational period.  This could have the effect of very calm weather on Uranus.  On the other hand, in the springtime, the weather on Uranus could be significantly more active, as the daylight/nightime ratio would at that time be just like any other planet.  If I am remembering correctly, Uranus was in somewhat of a summer orientation when Voyager arrived, and is in spring now.  If this is correct, could it not be possible that Uranus really does HAVE more visible detail now than it did when Voyager was in the neighborhood? 

[David Gray]

Problem is that a ‘cap’ was being recorded by several visual observers – before and after that encounter; including myself. But I have/am conceding that the feature may well have been a contrast effect – as I described on my previous post on here.

 

I feel that discrete lighter areas (storms??) at various surrounding latitudes closer to the limb at that orientation may have contributed to the usually off-pole cap-effect that was depicted, with perhaps a little contribution from the, albeit weaker, true cap.

 

Of course the planet has been observed becoming more active as it presented more equatorially.

 

A link to a post Voyager paper in a 1989 BAA Journal:   http://lnk.nu/articl....edu/1cick.html

(The UT for my 1969 Apr 7 drawing on there should be 23:50 - never observed that planet with the sun up)

 

Edit  Note:  Antares and Uranus at an altitude of <9º & 13º from here then (1985 June 2) (Lat. +54.7º).

 

Edited by David Gray, 14 August 2014 - 01:55 PM.

[David Gray]

I am attaching a Uranus observation from 1994 September 26 which also gives some indications of the usefulness of a W#15 filter with the planet. 

 

There was a friend observing with me, and without being specific, I calmly asked him if he had noticed a rather strong feature - he had, but admitted he was not mentioning it until I had said something.  So, without further inquiry, I asked him to sketch it: what he drew was very close to my impression, although he drew the feature virtually without any curvature, but also depicted the lighter part it circumscribed. 

 

The lighter patch in the no-filter view he struggled with and could claim no certainty with it nor any other detail (with/without filter) apart from limb shading.

 

My interpretation is that the filter brought out the light area so much that the dark border was, at least, a strong contrast effect.

 

Edited by David Gray, 14 August 2014 - 02:45 PM.

[azure1961p]

Ill definately be giving the W15 a try. I know fit a fact its terrific on bluer features on Jupiter like its festoons so it makes logical sense it'd be a fine choice for Uranus.  My w23a and 25 are too dense but the 15 sounds like the way to go.  Ill try the Neo too.

 

The  renderings make fine testimony.  

 

Pete

[azure1961p]

John,

 

thanks for the clarification.

 

Pete

[stanislas-jean]

Ill definately be giving the W15 a try. I know fit a fact its terrific on bluer features on Jupiter like its festoons so it makes logical sense it'd be a fine choice for Uranus.  My w23a and 25 are too dense but the 15 sounds like the way to go.  Ill try the Neo too.

 

The  renderings make fine testimony.  

 

Pete

I suggest you may use only the W8 or may be the W12, better for light transmission with an 8" and 350x.

Stanislas-Jean

[stanislas-jean]

I thought I read it theorized once that the blandness of the disc at the time of Voyager had something to do with the orientation of Uranus at the time; and by that I mean, not just the orientation toward the camera, but the orientation toward the sun.

 

Uranus' extreme axial tilt probably has an effect on the seasons far more extreme than that of any other planet.  When it is summer in one of Uranus' hemispheres, that is when one of the poles is pointed toward the sun, the area of the planet experiencing "midnight sun" conditions like the Arctic Circle here on earth would encompass most of that hemisphere; and likewise most of the other hemisphere remaining in darkness throughout the rotational period.  This could have the effect of very calm weather on Uranus.  On the other hand, in the springtime, the weather on Uranus could be significantly more active, as the daylight/nightime ratio would at that time be just like any other planet.  If I am remembering correctly, Uranus was in somewhat of a summer orientation when Voyager arrived, and is in spring now.  If this is correct, could it not be possible that Uranus really does HAVE more visible detail now than it did when Voyager was in the neighborhood? 

You may draw a line of 5% grey tone on a white paper and try to see it visually at a certain distance. Viewed: yes or no?

Now take picture of the white paper with the line and try to show the line. You will have to push the treatment parameters. Exhibited: yes or no?

Modify the light levels and repeat the tests.

Make a global status.

This will not easy and easily acquired.

Now for 5%, then down this to 2% this becomes a challenge.

Uranus surface is 54cd/m2 with features of 1" size and less on a 3.6" disk size.

This not jupiter or even venus, we had so many pictures also from shuttles featureless but with features also.

Stanislas-Jean

[David Gray]

Thanks Pete,

 

I have a Neodymium (2”) that I mean to try; tho’ not very good with Saturn I found - more drab than dull.

 

Reservations. however, with 8": Neo or #15.  Can but look - as opposed to being talked into or out-of using.  Suck it and see as I say

 

Dave.

[HellsKitchen]

I've lurking in these uranus threads with interest following the discussion about seeing features on it. I'll put forward my own observations.

 

Uranus Aug 28 2011. 8" F6 Newt. Seeing held up and got excellent view of the planet at 342x. I had to increase power, up to 480x I could see two very faint blips of light a similar distance approx north and south of the globe. Uranus itself was nice and crisp even at this magnification with only mild blurring in the seeing. CdC revealed these to be the moons Oberon (mag 14.2) and Titania (mag 14.0). Very faint for an 8" scope in an outer suburb location so was thrilled with my observations. Increasing mag to 600x again improved the visibility of the moons. Tried to eek out detail on Uranus itself, but the thing is just too small and thus very sensitive to even the slightest seeing disturbance, and this is ofcourse compounded by the extreme low contrast of any features that might be present.

 

Uranus Aug 12, 2011. 8" F6 Newt. Seeing was good enough that I could use 375x on the 8" dob with a nice crisp greenish-blue disk. Some people claim they can see markings on Uranus, I couldn't see any, just a uniformly coloured disk. The planet was located on the 'border' of a triangle bounded by 3 stars.... looking it up in Cartes Du Ciel, it turns out one of these "stars" is actually Titania, presently at mag 14.0! Not bad considering the moonlight and only 8" aperture. Difficult to glimpse ofcourse, but at 480x the moon was held quite easily when concentrating on the area.

[stanislas-jean]

I've lurking in these uranus threads with interest following the discussion about seeing features on it. I'll put forward my own observations.

 

Uranus Aug 28 2011. 8" F6 Newt. Seeing held up and got excellent view of the planet at 342x. I had to increase power, up to 480x I could see two very faint blips of light a similar distance approx north and south of the globe. Uranus itself was nice and crisp even at this magnification with only mild blurring in the seeing. CdC revealed these to be the moons Oberon (mag 14.2) and Titania (mag 14.0). Very faint for an 8" scope in an outer suburb location so was thrilled with my observations. Increasing mag to 600x again improved the visibility of the moons. Tried to eek out detail on Uranus itself, but the thing is just too small and thus very sensitive to even the slightest seeing disturbance, and this is ofcourse compounded by the extreme low contrast of any features that might be present.

 

Uranus Aug 12, 2011. 8" F6 Newt. Seeing was good enough that I could use 375x on the 8" dob with a nice crisp greenish-blue disk. Some people claim they can see markings on Uranus, I couldn't see any, just a uniformly coloured disk. The planet was located on the 'border' of a triangle bounded by 3 stars.... looking it up in Cartes Du Ciel, it turns out one of these "stars" is actually Titania, presently at mag 14.0! Not bad considering the moonlight and only 8" aperture. Difficult to glimpse ofcourse, but at 480x the moon was held quite easily when concentrating on the area.

Welcome to the club of observers having seen on Uranus !

Uranus is one of the planets that depends on the sky conditions more than the others. By the sky transparency and seeing conditions.

This is influencing the light level of the surface disk considering the sky transparency, contrast degradation by the seeing.

These parameters are sensitive on the final results.

Other points are to be considered:

uranus features are not constant in contrast

the contrast levels are faint to very faint.

the methane absorption rays on the light spectrum needs to be considered. The "contrast" of each ray is on relation with the wavelength, high in IR, low in NIR, very low in R, unsignificant in G and more in blue (but not null).

Visually we are interrested by the R channel that provides still albedo features accessible to observers (owning some personal characteristics or abilities with experience and training long term).

Now 200mm aperture is possible but hard to employ due to  the size of the planet at the eyepiece. A minimum size occuring an optimum surface brightness is needed for theorical perception. Optimum depends on the observer. For me 350-360 x is the optimum on uranus using a 200mm under a good sky transparency (m5.0 stars seen at the zenith). No less 6-7/10 images for keeping the contrasts at the eyepiece. This is easily checked watching a star near the planet and quoting the diffraction pattern under the said condition.

Hope this makes clear and hope you will participate on the survey, even with the 200mm. Publish your data on the Alpo japanese, I would say.

 

Now what can be shown in IR is not obligatory the carbon copy of the NIR pattern, then the R and so on. We should note some differences but not deeply.

Each wavelength of observation corresponding to a depth in the atmosphere.

Regarding the spots on current to-day, they are located on the upper layers of the atmosphere (as per the alert bulletin) sothat observations in pure R channel are not only welcome but requested. Visually the use of a yellow filter (W8-W12 max will be an help).

Stanislas-Jean

[azure1961p]

Hi Hell,

 

I enjoyed your reports!!!!

 

Ed Look ( another outter planets fan) also finds great success (seeing permitting) with very high power (600x) on faint moons as you too have done.  I'm guarded in the effect my 8" would have on the moons given my condo locale but its worth a shot anyway. Neptunes Triton is fringey under the same sky's so Im less than ESTATIC about the possibility of success.  Still, your post inspires and motivates!

 

Pete