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azure1961p
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Re: Personal Acuity once more new [Re: Asbytec]
      #6090791 - 09/19/13 10:40 PM

Thanks for the suggestions guys. I understand why the line is drawn where it is - Dawes for example could have easily seen beyond the 4.56/D thing but he had to call it just short of that to make it a empirical standard that could be applied with fair regularity in typical to good seeing conditions. Where as looking for the unique exception could be seen as wrought with environmental issues to say nothing of optical alignment and such.

I do like Wilfrieds suggestion of multiple masks of differing apertures. Saves me having to scour the sky for various doubles that must fit a very narrow separation and magnitude criteria.


Pete

Edited by azure1961p (09/19/13 10:41 PM)


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Asbytec
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Re: Personal Acuity once more new [Re: azure1961p]
      #6090838 - 09/19/13 11:16 PM

Actually, Pete, the Azure limit would be less that Sparrow. Right? We're not concerned with contrast between the discs, just elongation of them.

A hard limit would be set by diffraction where the PSF became as one. The Azure limit would be empirical. Right now, observation seems to suggest just a hair under 0.5R.


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azure1961p
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Re: Personal Acuity once more [Re: Asbytec]
      #6090874 - 09/19/13 11:43 PM

Lol well I would call it something other than the Azure limit but that's a kind suggestion. It'd not be a non limit like Sparrow but something just before that. Perhaps we can call it the Pigeon Limit?

- went out tonight - the forecast was good to great seeing. After an hour with the fan running the Altair was a nervous hair ball of morphing confusion. I hoped based in Cleardarksky.com that this would be my last chance for high res but ehhh - it looked like 5/10 seeing. Noghts like this top out around 173x- 200x. I think my sub second aspirations are going to sit on winters ice till spring thaw. Ill keep trying though.

Pete

Edited by azure1961p (09/19/13 11:44 PM)


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Sasa
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Re: Personal Acuity once more new [Re: WRAK]
      #6091175 - 09/20/13 07:08 AM

Quote:

Want just to point out that I do not consider very close doubles as good reference point for estimating personal acuity - the reason is simply a numerical: As measured separations are given in single digit decimals (exception are calculations of orbits but these are not necessarily more precise than direct measurements) this means that the "real" separation may be somewhere in between the rounding boundaries. This is no problem for example for 3 arcsesonds as this means "real" separation between 2.95" and 3.04" - an error range of in total 0.09 or 3%.
For an advertised separation of 1 arcsecond this means already an error range of 9% and for an advertised separation of 0.3" this means a huge error range of 30%. Conclusion: The smaller the separation the higher the measurement error range.
This is also a big problem for my RoT algorithm as for a 0.3" +5/5mag double this means a from the Dawes criterion derived range for the proposed aperture from 341mm to 464mm - the difference is a nice 120mm scope in itself.
Wilfried




Another good candidate to test you acuity is 65 Psc. I run on this double by chance in my 80mm scope. This is equal pair with optimal ~6mag brightness (6.3+6.3). It is not too close as well (4.3" in 2004 according S. Haas book).

I was able to see it as two close distinct needle-points in my 40mm Kellner eyepiece. This was providing 30x magnification in my 80/1200mm refractor. Which means that I was able to split two point sources at distance of about 130" (2.2'). Unfortunately, I did not have anything longer at hand to see how low I could go.


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azure1961p
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Re: Personal Acuity once more new [Re: fred1871]
      #6092762 - 09/21/13 01:36 AM

Quote:

Quote:

The Azure limit, somewhere between Dawes and Sparrow.




Nah - way beyond Sparrow. Sparrow is a wimp.
Azure limit is where the seeing interacts with the mirage effect, so you hope that what you're seeing is real beyond that hazy horizon of established possibility ....




Yeah but - that hazy horizon is so compelling! So we'll call it the Horizon Limit.

Alexander thanks got the suggestion and accounts.



Pete

Edited by azure1961p (09/21/13 01:38 AM)


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drollere
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Re: Personal Acuity once more new [Re: azure1961p]
      #6121355 - 10/06/13 09:33 PM

this is not really a complicated topic.

this web page adapts (from bob argyle's book on double star astronomy) an aperture mask that will produce interference bands at the 1.22*lambda/D interval. (so says argyle's text; i think it is actually just lambda/D. either way, it is the smallest interval your aperture can render clearly.) mount the mask, then use a zoom eyepiece or series of eyepieces to find the longest focal length at which the dark intervals are clearly visible. the page explains how to calculate your visual acuity from that test.

you can also use the diffraction rings around a bright star to the same end, and these are spaced as lambda/D, but the mask is much less affected by seeing.

the point to using either the diffraction pattern produced by a star or an aperture mask is that they create a standardized and highly contrasted visual stimulus.

once you launch yourself into "elongations" or "rods" or "near splits" then you are working with a nonstandard and visually ambiguous stimulus, and you're at the mercy of the widely recognized errors, fallibilities and quirks of the double star separation data you must rely on to define the separation you are using as the "test".

the larger problem is that there is no such thing as either a visual or telescopic resolution limit -- as rayleigh says, nobody knows what a "resolution limit" really means. a pair you can't resolve at medium magnifications you can often resolve at high, very high or absurdly high magnifications; a separation between two matched stars is visible, the same separation between two unmatched stars is not, especially as one star gets above 4th magnitude; i can easily see subarcsecond splits in 6th magnitude stars with my 140mm refractor but struggle to see several arcsecond splits in 11th magnitude pairs (weirdly, this is possible with averted vision) ... color matters ... seeing matters ... as does diffusion in the atmosphere and scatter in the optics.

all this makes the gesture of quoting one's personal visual acuity pointless, since your acuity, as an interval, is different in different situations. without a standard, explicit stimulus as the criterion, there is nothing to say.

i acknowledge the attraction of a fixed number and the idea of a "limit" as a useful guiding light and simple concept for learning how to look. but the goal is really to wean yourself off all fixed and rigid concepts and to become intimately familiar with your specific instrument, the highly variable landscape of things you are looking at, and the range of problems these things present to your observing skill.

if there is a resolution limit, then it is the number and variety of double stars you are willing to look at in order to learn how to look at double stars, and the amount of time you spend trying to crack difficult pairs before you give up -- a matter of persistence and experience.


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WRAK
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Re: Personal Acuity once more new [Re: drollere]
      #6122640 - 10/07/13 02:33 PM

Bruce, we have some hawk eyes on this board trying to reanimate the trodden path of resolving equal binaries by reaching for new frontieres beyond given concepts.
We have and hold in high esteem Rayleigh (138/D_mm), Dawes (116/D_mm) and Sparrow (106/D_mm) but have so for no criterion for detecting elongations. And this requires another type of personal acuity - not separating points or lines but recognising disks with deviations from being perfectly round. Ability to differentiate between hues of colors seems also relevant.
As far as I see we have now reached 62/D_mm for this task but only with singular observations and therefore missing statistical significance - lots of work still to do.
Looking forward.
Wilfried


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Asbytec
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Re: Personal Acuity once more *DELETED* new [Re: WRAK]
      #6123969 - 10/08/13 12:59 AM

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fred1871
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Re: Personal Acuity once more new [Re: Asbytec]
      #6124084 - 10/08/13 03:28 AM

Norme, I'm puzzled as to why you've reacted as you have - Wilfried's light-hearted comments, although also containing serious points to note, do not strike me as intended to be rude or insulting.

And I'm also one of the guys who claims to have achieved 0.5R on several binaries now. So, do I want to complain about "hawk eye" comments? - Nope. I can't claim the visual acuity (with a telescope) of WR Dawes, the "eagle eyed"; but seeing better than average (and better than I did before) does work in that direction. And 62/D, as you note, does fit around the 0.5R level. So it does not have to be personal; I expect quite a few of us will achieve 0.5R.

False positives? - I think every observer has the occasional one. I do. Other experienced observers I know, including some in other countries, do as well. The test is repeatability, first by oneself, and then preferably by someone else with suitable equipment. And, yes, there will be the occasional new record; I've noted RG Aitken, and more recently Christopher Taylor, going a little better than 0.5R, a level where one might expect an end point. So maybe there are aspects of a star image that show as "not quite single" when it's supposedly out of reach - SW Burnham made a few good calls on that with a mere 6-inch refractor, but he too had the occasional false positive. No insult; he was one of the greats.

"statistical significance" is about doing science rather than achieving personal records. Personal records are fine; I also try for them. But I see them as also being potential data points for analysis when enough of them accumulate.

Every time someone does an orbit calculation for a binary there are decisions on data points (in other words, questioning the observations). Look at the diagrams accompanying the orbits. Most errors are minor; a few quite large. In the case of the dreaded Gamma Equ it's clear there's a problem with the 1994 measure; but the guy who recorded it is one of the best of modern double star measurers. Typo? or what? It's just one of those things that happen to everyone sometimes.

The Haas project on doubles is another example of collecting data points for statistical analysis. The record smallest telescope for a given double won't be part of the final result if what's wanted is what can be expected for experienced but not "the absolute best" observers with various telescope apertures. Of course there could be a separate rule of thumb, or algorithm of likelihood, or whatever it gets called, that does fit the most exceptional results. Two versions. However I'd be surprised if there were no false positives in the data set, observations done in good faith, but which turn out to be off the chart - and too far off to be useful as relevant data.

The main problem we have with personal acuity is that there's a multi-factorial interaction between the optical complexities of the telescope, seeing, etc etc, and the various factors of the observer's particular eye-brain system. Have a look at the diagram in Suiter (2nd edition) which he calls the "wobbly stack" - all the factors that go into determining an image seen through a telescope.

Having said that - I don't think the issue is as subjective as Bruce seems to want to make it, looking at his recent comments. There do appear to be fuzzy limits, or areas of diminishing returns, for any observer with a particular telescope. Because the limits are fuzzy some will do better than others; some will improve their limits; but there are nevertheless areas beyond possibility.

Aitken notes that he and Hussey "found with the 36-in. at least five double stars with measured distances of 0.11" or less, the minimum for each observer being 0.09"...". He does not make this level of claim for observations with the 12-inch at Lick. That would not have been credible. But the 12-inch did better - relatively - by allowing the finding of pairs in the 0.25" to 0.20" range (later measured with the 36-inch). So the 12-inch allowed slightly better than 0.5R. Whereas, a claim of say 0.2R would not be credible (0.09" with the 12-inch).

Regarding Wilfried's statistical modelling, it is still a work in progress, so one can only say that a particular observation is a stretch (for example 5% likelihood - not impossible) - and with a revised RoT, perhaps 5% likelihood will be the case for more remarkable achievements. But it can also be that an observation, compared with current and definitely accurate data, is so far from that data that there's virtually zero likelihood of it being correct. We find out as we travel the journey.


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Asbytec
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Re: Personal Acuity once more new [Re: fred1871]
      #6124131 - 10/08/13 04:34 AM

I really tried to walk away from the comment at face value, but the connotation kept me coming back and wondering what was he really trying to imply. I understand what he said, but was he implying something else?

Quote:

...we have some hawk eyes on this board trying to reanimate the trodden path of resolving equal binaries by reaching for new frontiers beyond given concepts.




It's almost as if we'd be doing something wrong, that's the connotation that came across and set the tone for the rest of his comment. Statements like this can come across wrong, almost condescending - which drew my ire.

When you associate what appears to be a direct reference to an enjoyable, difficult, and highly probable success with pronouns such as "some," (as in "ssooommmmee people, whew!"), who observe "beyond given concepts," "trying to reanimate," a "trodden path," while "reaching for new frontiers," certainly do not appear to be light hearted. It comes across as a well disguised insult - in context. Taken in that context "hawk eyed" does not sound like a compliment, either. Even a comment as simple as "on this board" seems suspect, as if it doesn't happen on other boards that are what? More reliable?

Any single comment above would not mean anything, per se. Put all those words together and a context develops. One may be forgiven for wondering what he was really trying to say. Is that poetry? I took offense as an amateur "on this board" who apparently tried to "trod" down some path "beyond given concepts", beyond which observation is apparently impossible, "reaching new frontiers" that are apparently available only to those established observers who, by the way, have observing credibility. Which seems to imply "some," "on this board" probably don't, I guess...

I deleted my response above for the sake of the topic. I'd hate to see it get locked going "beyond given concepts" in the rules.


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WRAK
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Re: Personal Acuity once more new [Re: Asbytec]
      #6124185 - 10/08/13 06:33 AM

Norme, you have proven yourself as keen observer. My wording may include a dash of irony you certainly can therefore take with grace I hope.
The idea of an elongation criterion has without irony some appeal to me. Sissy Haas uses the magical prime 11 as number of required observations for confirmation - this number could be used also here as threshold for statistical significance. Just a proposal.
Wilfried


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Asbytec
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Re: Personal Acuity once more new [Re: WRAK]
      #6124202 - 10/08/13 06:50 AM

Wilfried, I completely understand the statistical nature of your project and sticking to Dawes concepts. You're looking for a rule of thumb, not outliers. That makes sense. I fully support your work and have worked hard to discuss and assist, even trying to understand your reduced resolution with larger CO.

What struck me was not picking up on your irony, but rather the idea 62/D is somehow impossible and therefore open to ridicule. That it is somehow a new frontier beyond given concepts that makes it sound like I am just imagining things while helplessly trodding down some path reanimating star images in my head at will.

I apologize if I failed to pick up on your intent. Your comment confused me and made me wonder what you were really trying to say. I spent most of the day wondering.


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brianb11213
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Re: Personal Acuity once more new [Re: fred1871]
      #6124224 - 10/08/13 07:18 AM

Quote:

Aitken notes that he and Hussey "found with the 36-in. at least five double stars with measured distances of 0.11" or less, the minimum for each observer being 0.09"...". He does not make this level of claim for observations with the 12-inch at Lick. That would not have been credible. But the 12-inch did better - relatively - by allowing the finding of pairs in the 0.25" to 0.20" range (later measured with the 36-inch). So the 12-inch allowed slightly better than 0.5R. Whereas, a claim of say 0.2R would not be credible (0.09" with the 12-inch).



Yeah ... but don't forget that being able to split a double is completely different kettle of fish to being able to measure it. Seeing effects are also important, I very much suspect that even at the best sites the seeing would never allow the diffraction pattern to be clearly & consistently resolved with 36" aperture (without the aid of adaptive optics) whereas a 12" scope would struggle far less with waveform distortions contributed by our unstable atmosphere.

As for the accuracy of measures - as the seperation decreases I would expect the error in measuring position angle to increase, whereas the (absolute) error in measured distance should remain pretty stable. I would hope that, when measures are made for the purposes of orbit determination, some effort is made to estimate the errors involved, but I've never seen the estimated errors catalogued.


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Asbytec
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Re: Personal Acuity once more new [Re: brianb11213]
      #6124290 - 10/08/13 08:24 AM

Wilfried, one of the amazing things about having a 6" in the tropics is it appears to respond very well to seeing conditions. This, more than anything else, seems to have rekindled a love for observing and exploring planets and doubles, particularly. I have always been anal retentive with collimation and have become that way with cooling to ambient.

When you put those conditions together with diffraction limited optics, observing becomes a real treat. It's easy to become an optimist and to really press everything the scope, eyes, the sky, and the laws of physics can offer. It's easy to ask how far one can go, can we reach some diffraction limited boundary since we really don't worry much about battling those dancing rings and dirty images. You still have to wait for it, but it comes more often.

When one observes in a diffraction limited realm, even with a modest aperture, the results are often stunning, pleasing, and worth shouting about. Jupiter simply impresses and doubles seem to respond well, too.

I still have no idea what my own personal acuity is, I assume it's average maybe less. But, I just cannot express enough the appreciation for great skies and what you can do with them. This is one reason your CO observations were so interesting and why I felt the seeing might have been the appropriate approach to understanding why resolution fell off in conditions that were likely less than diffraction limited.

I dunno, I guess the point is seeing is so important. When observing is diffraction limited from 3x/inch to 50x/inch and even higher, there is just so much one can do. It's a realm where MTF makes sense and scopes perform as advertised. The laws of physics don't deviate much from the real world where people tend to doubt those laws, to argue over MTF as unrealistic compared to what they observe.

When seeing is diffraction limited, those laws become apparent, consistent, and even limiting. But it's beautiful thing to behold, even those ugly obstructed Airy patterns when they are dead still are amazing to look at - to know the best possible performance awaits that night. It's a realm where one's personal acuity and equipment is put to best use and success is a patient observation from reality.

Any success I achieve is always credited to the conditions, collimation, cooling, and a descent scope that make success more possible rather than a chore. In such conditions, one should be able to bump up against what is physically possible in a given aperture. That's exciting and inspiring. It's like surfing that perfect wave and living to talk about the experience.

Sorry for rambling...just reflecting.


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fred1871
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Re: Personal Acuity once more new [Re: brianb11213]
      #6124430 - 10/08/13 09:35 AM

Quote:

Quote:

Aitken notes that he and Hussey "found with the 36-in. at least five double stars with measured distances of 0.11" or less, the minimum for each observer being 0.09"...". He does not make this level of claim for observations with the 12-inch at Lick. That would not have been credible. But the 12-inch did better - relatively - by allowing the finding of pairs in the 0.25" to 0.20" range (later measured with the 36-inch). So the 12-inch allowed slightly better than 0.5R. Whereas, a claim of say 0.2R would not be credible (0.09" with the 12-inch).



Yeah ... but don't forget that being able to split a double is completely different kettle of fish to being able to measure it. Seeing effects are also important, I very much suspect that even at the best sites the seeing would never allow the diffraction pattern to be clearly & consistently resolved with 36" aperture (without the aid of adaptive optics) whereas a 12" scope would struggle far less with waveform distortions contributed by our unstable atmosphere.

As for the accuracy of measures - as the seperation decreases I would expect the error in measuring position angle to increase, whereas the (absolute) error in measured distance should remain pretty stable. I would hope that, when measures are made for the purposes of orbit determination, some effort is made to estimate the errors involved, but I've never seen the estimated errors catalogued.




Agreed - the limitation for the 36-inch is essentially the seeing conditions. And the PA can be expected to be more difficult with decreasing separation. The main point of quoting Aitken had to do with (1) getting a bit beyond 0.5R with the 12-inch and (2) suggesting that for particular telescopes, no matter how good the observers, there are definite limits to possibilities, whether an optical limit from the instrument size (12-inch) or from the atmosphere (36-inch).

Original papers of measures sometimes give the estimated errors, indirectly, by recording the full list of measurements that go into the final measure quoted. A large scatter is not a good sign.

A lot of recent measures are by speckle interferometry or with adaptive optics on large telescopes; these can be expected to be of higher typical accuracy, especially with very close pairs, compared to older filar micrometer measures. Looking at these newer methods measures, as recorded on 6th Orbit Catalog diagrams, suggests that that is the case. And there are some science papers published that discuss the accuracy levels to be expected from the modern techniques. Both PA and separation should be more accurate - the one issue is that sometimes, with speckle work, there's an ambiguity of quadrant; usually this can be resolved from the pattern of previous measures. It was occasionally an issue with equal pairs in the past if they were not measured often enough in relation to the orbital period.

When an orbit is calculated, the residuals for the measures are part of the data pool. These may become useful in developing weightings of measures when a new orbit calculation is made. Usually, the first orbit determination is approximate, being refined over time as more measures become available. A paper giving an orbit calculation often enough lists the measures and their residuals relative to the orbit as calculated. Notice also the weightings given in the 6th Orbit Cat on how close to definitive an orbit seems likely to be.


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WRAK
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Re: Personal Acuity once more new [Re: Asbytec]
      #6124480 - 10/08/13 09:57 AM

With elongations we certainly leave firm ground but may be this makes it interesting all the more. And yes - measurement errors are increasing critical for very small separations.

To contribute empirical content for an elongation criterion I searched my observation log for my so far "best" elongation:
Last July STF1967 (Gamma CrB, HIP 76952) 0.6" +4.04/5.6mag. Short orbit, separation currently according to 6th orbit catalog 0.56". With 140mm and x280 magnification elongation at 2 o'clock with later check position confirmed.
Means 0.56*140=78.4/D_mm.
Wilfried


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azure1961p
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Re: Personal Acuity once more new [Re: WRAK]
      #6124546 - 10/08/13 10:29 AM

Per Fred:

"Norme, I'm puzzled as to why you've reacted as you have - Wilfried's light-hearted comments, although also containing serious points to note, do not strike me as intended to be rude or insulting. "

That may be Fred but the comments lately here have been laced with sarcastic doubt. Its not a Norme thing- Ive seen it elsewhere aimed at different people. And some getting understandably heated about it.
Cotts took the time to (very non-confrontationaly) state a few pointers on the matter.

Re animating a well trodden path or whatever reads very clearly like: jump starting a dead horse for not real purpose or gain, ie; a waste of time. There's a better way to state it. Look I have my doubts about others observations - not your or his and Ive even been too vocal but - ehh there's a better way.

Pete

Edited by azure1961p (10/08/13 10:36 AM)


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WRAK
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Reged: 02/18/12

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Re: Personal Acuity once more new [Re: azure1961p]
      #6124860 - 10/08/13 12:45 PM

Pete, thanks for the hint - I will try to keep my language straighter and express any doubts directly or avoid a comment at all.
Wilfried


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Asbytec
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Re: Personal Acuity once more new [Re: WRAK]
      #6126058 - 10/08/13 11:00 PM

Wilfried, again, I apologize for not picking up your poetic irony - which was pretty good, by the way. It came across as mocking and I was already in a foul mood. So, I take some blame for applying the improper context to your choice of words. I was expecting some resistance to 62/D, anyway, especially, as Pete said, in light of some of the references in earlier comments. So I took offense when I saw what appeared to be my own observation referenced in a perceived context of mocking. I was beside myself in short order.

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WRAK
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Re: Personal Acuity once more new [Re: Asbytec]
      #6126350 - 10/09/13 04:28 AM

Norme, thanks. This settled we can return to the progress of sampling observations reports for observed elongations for equal bright (delta_m up to 1) or nearly equal bright (delta_m up to 2) binaries with positive check for the indicated position. With your Chi Aql and my STF1967 we start with two reports and a range between 62/D_mm and 78/D_mm.
I will do some search on this forum and check literature. Maybe Fred will provide his 0.5R observation as others as well their "best" elongation observation.
With some reports more we should get a feeling for a reasonable criterion for detecting elongations - as always with some bandwidth for individual variation.
Wilfried


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