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azure1961p
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: Rich (RLTYS)]
      #5961820 - 07/09/13 08:25 AM

Stan,

There's no pecking order of whose a viable poster here on this thread. I stated pretty to the point why there was contention here and what the points centered around. I'm actually a good person to comment here maybe not the best but not the last. You need to take a step back.


Pete

Edited by azure1961p (07/09/13 08:35 AM)


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David Knisely
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: krakatoa1883]
      #5962298 - 07/09/13 02:30 PM

These drawings definitely highly exaggerate the width and contrast of any visual detail that might possibly be visible on Venus. Most of the time when I view Venus in eight to ten inch apertures, the disk is pretty much blank except for the slight soft phase shading that is easily visible towards the terminator. The only times that I have seen anything on the disk is when Venus is considerably closer to us than it was late last month, with a phase approaching 50% illumination. Then, I can sometimes see a few very very fine narrow very low contrast wispy markings that seem to flow parallel to each other but overall show some curvature or slight sinuosity sometimes. However, even the slightest seeing variations tend to render them invisible even in a deep blue or violet filter. Most of the time (even under good seeing), I see little to nothing on the planet, so markings are not always present. I observe Venus in the daytime or during bright twilight just after sunset for the most part, as then, it is high enough above the horizon to be in an area of fairly stable seeing. The markings I have glimpsed on Venus are very narrow, wispy, and hard to see even in a 10 inch, so I have some doubts they would be visible in only a 120mm aperture.

I have drawings I made as a beginner in the late 1960's using my 2.4 inch refractor which show a large-scale "Y" shaped patch on the planet when it was in a gibbous phase. I have not seen this repeated since then in my larger scopes, so I have at least some doubts that what I recorded may have been much more than just a visual contrast illusion. Clear skies to you.


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: David Knisely]
      #5963397 - 07/10/13 01:20 AM

Next time at your eyepieces for Uranus!
Effectively David the features reported are given with a strongly amplified contrast. Well seen.
Stanislas-Jean


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krakatoa1883
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: David Knisely]
      #5963520 - 07/10/13 05:04 AM

The visibility of the dusky markings of Venus atmosphere is a much debated question that can be traced, for example, through the JBAA reports. It is beyond doubt that they can be visible under favourable conditions even through small instruments, however the slightest ondulations of the atmosphere tend to obliterate these subtle features generating illusory details. Their observation and reporting requires considerable skill and experience and should always be considered with much caution. In some instances, however, more contrasty details can be easily seen, this occurred for example during the early spring of 2012 when the visible counterpart of some prominent UV bands could be traced through blue and even green filters.

After almost twenty years of observing and collecting Venus observations for the UAI, it is now my opinion that the visual observer should concentrate most on those details that can be seen with certainty at the eyepiece, that is the phase, the ashen light, the bright caps, the terminator shape etc. leaving the study of the dark bands to the CCD imagery which is more effective at the shortest wavelengths.


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brianb11213
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: krakatoa1883]
      #5963543 - 07/10/13 05:46 AM

Quote:

The visibility of the dusky markings of Venus atmosphere is a much debated question that can be traced, for example, through the JBAA reports. It is beyond doubt that they can be visible under favourable conditions even through small instruments, however the slightest ondulations of the atmosphere tend to obliterate these subtle features generating illusory details. Their observation and reporting requires considerable skill and experience and should always be considered with much caution. In some instances, however, more contrasty details can be easily seen, this occurred for example during the early spring of 2012 when the visible counterpart of some prominent UV bands could be traced through blue and even green filters.



Agreed. Personally I consider Venus to be a most difficult target to observe visually, any markings which are visible being very subtle and almost impossible to draw without the drawing showing far more contrast than is actually visible.

Smaller apertures might actually have an advantage in tending to have more contrasty images than larger apertures, the contrast gradient being reduced by increased magnification and the eye being overwhelmed by the extra light delivered by a larger objective. Visual observation in daylight is not so effective as diffuse skylight reduces the already minimal contrast. In my experience, anyway.

Quote:

After almost twenty years of observing and collecting Venus observations for the UAI, it is now my opinion that the visual observer should concentrate most on those details that can be seen with certainty at the eyepiece, that is the phase, the ashen light, the bright caps, the terminator shape etc. leaving the study of the dark bands to the CCD imagery which is more effective at the shortest wavelengths.



This is getting very close to saying that, in this age of advanced technology, visual observations no longer have a value. I'm not sure this is true. At any rate, modern visual observations help to interpret historical visual observations: sure, the eye can be and often is tricked, and this does need to be factored in.


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krakatoa1883
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: brianb11213]
      #5963594 - 07/10/13 07:20 AM

Quote:

This is getting very close to saying that, in this age of advanced technology, visual observations no longer have a value.



being myself a visual observer nothing could be more distant from my thought. Visual impressions and drawings are still very important in order to give continuity to the historical observations, as you have pointed out. Nevertheless if the scope of the observation is the study of Venus atmosphere digital imaging in violet, UV and IR is far more effective and useful than any drawing however accurate it can be.


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krakatoa1883
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: brianb11213]
      #5963610 - 07/10/13 07:37 AM

Quote:

Visual observation in daylight is not so effective as diffuse skylight reduces the already minimal contrast. In my experience, anyway



I think it depends on several factors. For observing with dark blue and violet filters I always found more effective a bright twilight with the Sun just below the horizon, otherwise I prefer to observe in full daylight.


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: krakatoa1883]
      #5963714 - 07/10/13 09:41 AM

If you observe venus since 20 years, personnally it 's since the 80ies.
Personnally I cannot agree with your experience because depending on what you did personnally and from data given by other observers that usually we have difficulty to evaluate their limits.
This is reason why the evaluation of documents needs other assessments. For illustrating this refer to the "famous" forum issued here for Uranus. You will know, a little, my approach that can apply for most of the subject.
I suggest you perform personnally some tests on your own eyes in a laboratory equiped with mesure machine. Where I am working they have these means that allow to test viewing under color channel, light levels, resolution grids with different contrast levels.
This is very instructive to get results about. After this is changing views in some manners.
The poorness of the contrasts observed on some planets, venus easier than Uranus, makes also the need of some researches about the actuallity of contrast levels existing on planet surfaces. By literature publications, the Havard Library (free access), data published by professionnals may help to fix these data. These planets are not feature free at conclusion and exhibit them at confidential levels.
You may also yourself perform these researches.
Now what is done on commissions, etc..., or organisation is subject by nature to discussions. Why, judgements are set by coordinators having their own experience (what can be reported by others is not what is reported by yourself). The collection of data from other observers are not representative of what can be generated individually on such margin difficult subjects, the differences between individuals being too large for making a valuable consensus.
Venus and Uranus are good examples for illustrating this.
Regarding such planets, when it is existing 2% contrast levels featuring ON planet:
- at the eyepiece you will get a lower level, correct?
- with great aperture, a 40" for example, you will get at the eyepiece lower than 2%, and what you will get will be washed by the seeing quickly mostly.
- with moderate aperture you will get a contrast level still accessible, mostly not washed by seeing.
- any scope will not outperform the 2% level except with a ccd camera but under skill hands (artefact are not welcome).
- Mr Yamazaki performed tests by imaging for featuring venus in different color channels, including unvisible where on a day from hour to an other the fine structure revealed was quickly changing, but featuring was reported in all color channels.*
For a conclusion the venus vision is lead by the personnal equation of observers able to capture low contrast levels, so a matter of personnal threeshold that allows captures or not or only partially.
Last point, on venus any magnification is not obligatory suitable. It is necessary to adjust the magnification for getting the best signal to noise ratio in order to make readable the planet surface. Ligth glare is the noise with adding the seeing and the optical aberrations plus the optical acuracy (by the optical design also). The rigth way to see if the S/N ratio is OK, this is light level of the planet background to be adjusted in first and then sligthly modified with regards to the seeing level. If the ligth is a little too high, avoid the observation because the glare will help the seeing to wash the few features more quickly.
Hope I am clear enough.
Stanislas-Jean


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krakatoa1883
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: stanislas-jean]
      #5964003 - 07/10/13 12:46 PM

Quote:

Hope I am clear enough.



It's all but clear. It seems that your are concluding the followings:

1. the details reported in your drawings are real but only few privileged humans - including yourself - can see them

2. as a consequence of point (1) it is useless to compare drawings coming from different observers as they all have different "personal equations". If true this would be the death of visual astronomy.

Well, let's assume your point, we are not discussing about theology, may be you're right and I'm wrong. We all know that some individuals, including may be yourself, are more sensitive toward the violet and the UV than the average people (see for example Dall H., JBAA 75, 1965) and therefore able to see details that remain inaccessible to most observers. In these fortunate cases it should be possibile to find some correlation between what one can see visually at short wavelenghts and modern CCD images in the UV. Can you show us something of this kind based on your own drawings ?


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azure1961p
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: krakatoa1883]
      #5964242 - 07/10/13 03:17 PM

See there's the catch 22...

I'm of the mind some observers preload their expectations with CCD imaging or even satellite - play with the numbers a bit to find some things are possible in theory at the threshold of vision then summarily realize it all at the eyepiece and further more have graphs and math to *prove* it. And that's not to say the graphs and equations are false but merely sterile of the environmental and physical effects that are part of even the best observation. I would venture to say that asking some one to produce a drawing of a feature prior to pre suggestion by digital imaging is a tall order - particularly in this case.

Pete


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idp
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: azure1961p]
      #5964296 - 07/10/13 03:46 PM

Stan,

You have seen things we people would not believe... Uranus's bands with a C8... and watched markings no one ever saw, all over the glittering disk of Venus.

Good for you, why would you need our approval? Keep watching and sketching, so that those moments will not be lost in time like tears in rain.

Time to let this thread die.

Ivano

Edited by idp (07/10/13 03:47 PM)


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krakatoa1883
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: idp]
      #5964347 - 07/10/13 04:25 PM

Agreed, Ivano, there is no reason to go further.

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azure1961p
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: krakatoa1883]
      #5964693 - 07/10/13 08:31 PM

Ivano - I applaud your qoute. Hauer made it one of the most moving moments .

Pete


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: azure1961p]
      #5965107 - 07/11/13 01:52 AM

Pete you applaud.
Others seems to be responded about a certain approval.
When it is done something unusual, the common reaction is to say as Pete impossible.
"Impossible" is not an objection but an opinion oftenly not built and settled on facts and results.
Sothat it is perfectly normal to expose some views in order to explain a situation which is by nature difficult to approach. Human reaction for a guy on defense situation who has to defend own views (like a guy in street injured by others and explains why he was injured and so begs pardon).
For the few, sorry for shaking some dust.
I don't know if you are confortably seated in views, if this is the case this is just an hobby. Right? as for the most.
No objection against this is free activity, but when something is reported, please have a carefull look on.
We knew somany people in past having performed something unusual (here also at CN, not speaking me) completly scrambled by usual views.
Try to do different approaches, this will make progressing.
On venus the Alpo japanese is a good example for searching comparisons.
On uranus, there was in past observers who did something consistent with the results we know and opinions (because opinions only) against.
The big concern is when somebody declares "impossible" with opinions so oftenly not supported by consistent experience, tests and knowledge.
The references frequently given consisting in the comparison with space shuttle results is strange because when you start some documental researches we discover some different noises (they are research reports, observationnal results, tests, shuttle status results, etc...).
My refrences are not common magazines (no names here).
Now for images comparisons go to the alpo jpn site.
May I suggest you test also your eyes, this is instructive in addition.
Last point, it is interresting also to have exchanges on these kind of subjects because experiences exchanged on "marginal" subjects bring a lot for discovering who is who in terms of experience.
For a forum which exposed scopes different results and the question why, this is far away.
Stanislas-jean


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Cotts
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: stanislas-jean]
      #5965807 - 07/11/13 02:29 PM

Stanislas: I just want to see if I understand what you are showing in your sketches.

. Please correct me if I'm wrong.

June 29, around 1700 UT (+/- about 30 minutes) so about 3 to four hours before sunset with Venus as much as 45 degrees above the horizon and around 30 degrees from the sun. You are observing in bright sunlight.

The diameter of Venus is 11 arc seconds at the time of observation. You show markings that are clearly smaller than 20% of the diameter - in the 1" to 1.5" range and smaller as well.

You made these drawings through some cirrus cloud.

You are using 100mm and 120mm telescopes.

You are purposely exaggerating the contrast of the features in your diagrams.

Is that mostly correct?

Thanks,

Dave

Edited by Cotts (07/11/13 02:33 PM)


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Cotts
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: stanislas-jean]
      #5965812 - 07/11/13 02:32 PM

Quote:

Please have a look on
http://alpo-j.asahikawa-med.ac.jp/kk13/v130706z.htm
since for the 1-4-5-6th last.
S-J





Are you using your own diagrams to support the accuracy of your diagrams??? The link only goes to some sketches by you from early July.

Dave


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Cotts
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: stanislas-jean]
      #5965827 - 07/11/13 02:45 PM

Quote:

I donot expect some issue with seeing effects.
There is nothing to do under the conditions of use.
See the link
http://alpo-j.asahikawa-med.ac.jp/kk13/v130620z.htm
for comparison with a short 120 achromat here better than the said semi-apo (120ED is not an apo).
The lacks observed in B and R channels are, on same channels the 100mm achromat allows to see more (here a TAL100mm).
Sothat my conclusion is that these apos are not suitable for use on planets except for getting pleasing views in IL that is.
This is a little disapointing and with regards to the expense done for few (being the fifth apo tested from 100, 110 now 120ED).
I will continue the comparison with the MN127mm Intes and the venerable 154mm newtonian, largely less expensive.

Brian, don't know if spherochromatism can be the answer because when practicing the ronchi with color filter B and R (with a grid of 10lp/mm) spherical aberration is not appearing sensitively on the 120ED. But this is an explanation. I think the residual chromatic aberration in these channels are not negligeable in fact but don't know how to measure this effect with reliability. May be the roddier can bring something and investigate more this.
Tests are continuing. Thanks for your posts.
Stanislas-Jean




Are you suggesting that the linked infra red photographs correlate or 'prove' that your sketches are accurate? The pictures are usin an IR pass filter which only admits light longer than 700nm which is a region the human eye cannot see and for which refractive telescopes are not corrected.

Dave


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: Cotts]
      #5966734 - 07/12/13 01:50 AM

Conditions are noted with the sketch, this is observations in daylight effectively. The same scope characteristics cannot allow to see after the sun set time, glaring being too annoying (167x, 100mm).
S-J


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: Cotts]
      #5966752 - 07/12/13 02:07 AM

Don't understand what you mean by diagram.
I donot use the standard form issued in BAA or Alpo.
A 2" size is not suitable for getting an overall picture of the disk. Here this is 1" and already with some difficulty for fullfilling.
If you consider a feature size as the same way it can be evaluated on pictures, this is a wrong approach.
To-day the disk size is 11.4" observed with 100mm this means 10 lines possibble at the theorical dawes limit. This is confortable. Do you believe people observing encke around few% contrast level in a 10" as well?
The equation is the following: 50" around eye resolution with ligthing under 1 lux on feature 5% contrast(the machine doesnot go under).
Make the extrapolation.
For documents you may investigate for the past elongations where several apertures where used.
For the past ones, you may find at Lowell obs. originals from the 80ies (given to CF Capen at times for Mars) and Alpo US for Venus, if archives are well standed.
At the BAA for the same periods and recently, all.
Up to you to have a look on.
Returning on the recent issued on the Alpo jpn, you may note that the densification became harder with the disk size increasing. 5% more size seems negligeable but not when a threeshold is passed, this is not linear effect, but at a certain size diameter the feature gain is not effective apart the fact using a bigger apeerture under perfect conditions.
S-J


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stanislas-jean
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Re: Venus on 29th June: results with 100achro/ 120ED new [Re: Cotts]
      #5966760 - 07/12/13 02:16 AM

Even at 700nm, the features reported are clouds nature, not ground (even at 1m).
470C make the threeshold wavelength of 1.5m if i remember well.
So we can consider or could consider that above 700nm what is reported should have similitudes with what can be reported with a W29 filter.
This is harsh to say as well for saying 1m observations are related to ground features, but in fact only similitudes are revealed.
Has Venus distinct atmospheric layers? The external layer (UV, blue green) is one, for the rest this is a thick layer with differential speeds, according what we can read about.
S-J


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