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theskyhound
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Reged: 03/10/06

Loc: Cloudcroft, New Mexico
Re: Research project - Limit for uneven Double Stars new [Re: drollere]
      #5364771 - 08/12/12 01:55 PM

I see this issue all the time, because I use these models in my software. I model everything; the faintest star you can see, how difficult it is to detect a faint fuzzy, how difficult it is to split a pair, and I predict SNR for images.

The pedants always say the same thing: there is no way you can do that accurately, particularly for things near the limits. And they are right! But here's the thing: just being in the ballpark is enormously useful in real world applications.

As a start, these algorithms allow you to clearly state those things that are simple to predict. How do most people pick easy pairs? By using pre-compiled lists of stars that others have observed. But this is usually just the tip of the iceberg of objects available. So everyone ends up observing the same subset of the available pairs again and again. Now imagine a program that looks at every pair of stars that has been cataloged, looking for pairs that are easy to split in a 4-inch telescope. Making that particular prediction is not all that difficult and the results will be fairly accurate. If you toss in a filter to select objects that are well placed on a given evening, then you have something quite useful. I can't stress this enough: the emphasis is always put on the most difficult circumstances to predict, but in fact most of the utility comes from being able to predict things that are more easily predicted.

For those things that are difficult to predict, where the prediction is questionable, a predictive algorithm is still quite useful. The algorithms tend to break down at the edges of perception; in other words they break down for the pairs that are difficult to split. This is a happy coincidence. After all, if we could accurately predict whether or not a challenging pair can be split under every conceivable circumstance, then there would be little point in going out to the telescope to try. For the challenging pairs the very point of observing them is to try to push your limits, not knowing if you are going to be successful. If our predictive algorithm says a pair is going to be very difficult to split, sure, it may not be perfectly accurate. In truth the pair may be easier than predicted, or it may not be splittable at all. But if used correctly, the algorithm can still predict which pairs are challenging, regardless of whether or not the detailed prediction is accurate.

So I very much support the efforts of people like Haas! In my world these models aren't just an academic exercise, or something futile. If you start with these algorithms, and toss in some cleverness and ingenuity, they can in fact be extremely useful in real world applications. In particular, they can be an invaluable tool for selecting objects to observe that are appropriate for a given telescope and conditions.

Clear skies,
Greg


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azure1961p
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Reged: 01/17/09

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Re: Research project - Limit for uneven Double Stars new [Re: theskyhound]
      #5364864 - 08/12/12 03:02 PM

Hi Greg,

I agree no formula here is perfect and there will be a lot of perception issues between observers but it does, or potentially does, leave a fair *jumping off point* from which to at least have some sort of handle on the challenges. Ill find it in bad taste if after a group compilation the *limit* is merely a banner for one persons name. Havent know this to be Haas at all but mentioning it regardless.

Pete

Edited by azure1961p (08/12/12 03:04 PM)


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WRAK
scholastic sledgehammer


Reged: 02/18/12

Re: Research project - Limit for uneven Double Stars new [Re: azure1961p]
      #5367741 - 08/14/12 05:00 AM

Any realistic "formula" can only give a probability for splitting as even an easy double can be tricky under specific circumstances not covered by the formula. So with a reasonable big number of observers for a specific double you get a percentage of splits that can be used as probability - means that even your own yes or no can be the other way around next time.
But certainly aperture, separation, magnitude delta and seeing are not enough relevant criteras - magnitude loss due to light pollution, altitude depending on location and time of observation and yes focal length will play a role here. And seeing should best be split in stability and transparancy. So this gives in total about 10 parameters and I am quite sure probabilities calculated on such a frame would be of high reliability.
Wilfried


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Ed Whitney
sage


Reged: 07/08/10

Loc: Palm Coast, Florida
Re: Research project - Limit for uneven Double Stars new [Re: WRAK]
      #5376720 - 08/19/12 10:36 PM

This has been very interesting reading. However, even thou there will be many reports and observations for Ms Haas to evaluate and then come to some sort of final conclusion, do feel that this is a worthwhile project.

It might just turn out to be that the journey was more important than the result. And then, there could even be a totally unexpected "bonus" or revelation that was never dreamed of at the start.

In any case, I'm on board to try to help Ms Haas.


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KirtErie
journeyman


Reged: 09/16/12

Loc: Alpena, MI
Re: Research project - Limit for uneven Double Stars new [Re: Astrojensen]
      #5441292 - 09/26/12 09:34 AM

I get my copy each month from the local library. If your library does not have it on the shelf, ask if the interlibrary loan system can get one delivered.

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nrivard
newbie


Reged: 09/25/12

Re: Research project - Limit for uneven Double Stars new [Re: theskyhound]
      #5442661 - 09/26/12 11:15 PM

For those who are interested to participate in this project, I built a web site that gives all the information you need. Please note that the list of pairs published in S&T has some errors and is incomplete. Sissy has sent many updates since then. I also prepared some sky maps for those who dont have GOTO scope like me.

http://unevendoublestars.wikispaces.com/home

I also hope you become friends of the facebook page, so you can stay up to date with the latest changes on the wiki site.

http://www.facebook.com/pages/Unevendoublestars/226255637503049

Enjoy!


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Rich (RLTYS)Moderator
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Reged: 12/18/04

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Re: Research project - Limit for uneven Double Stars new [Re: nrivard]
      #5442977 - 09/27/12 06:13 AM

Thanks, excellent site.

Rich (RLTYS)


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drollere
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Reged: 02/02/10

Loc: sebastopol, california
Re: Research project - Limit for uneven Double Stars new [Re: theskyhound]
      #5443240 - 09/27/12 10:24 AM

Quote:

The pedants always say the same thing: there is no way you can do that accurately, particularly for things near the limits. And they are right! But here's the thing: just being in the ballpark is enormously useful in real world applications. ...



well, as one of those "pedants" i'm happy to concur with your agreement that "we" (i) are correct in our skepticism. however, you seem to concede a point while denying it, as prediction that doesn't work is still "enormously useful", which leaves me unclear as to what you want to say.

Quote:

How do most people pick easy pairs? By using pre-compiled lists of stars that others have observed. But this is usually just the tip of the iceberg of objects available. So everyone ends up observing the same subset of the available pairs again and again. ...



i wouldn't agree that everyone ends up in a rut ... i believe wilfried is embarked on a campaign of rummaging through obscure stars, and there was another discussion here of jonckheere doubles, a catalog that rarely make it into the "top 500" lists. but this is really a digression from your point, which is a defense of "predictive" algorithms as a statistical vade mecum that can lead observers away from the hackneyed into the wide unknown.

really? if you only date those few persons that you "predict" will give you a good night kiss, then you've taken a hell of a lot of excitement and adventure out of dating; and similarly if you only look for double stars that you "predict" in advance will be "kissing", then you've merely fallen into a more elaborate and ritualistic form of routine, and you have not really addressed what seems to be your complaint, which is that the observer should challenge himself with something genuinely novel or unknown. you've just replaced a rut of consensus with a rut of "prediction", which seems to mean a consensus as to how doubles look without actually looking at them. at least, looking was how those lists you disparage were compiled.

the crux is that you seem embarked on the project of telling me what i will see before i've actually looked at it, rather than telling me why something may be difficult to perceive when i try to look for it, which is a very different type of guidance.

Quote:

The algorithms tend to break down at the edges of perception; in other words they break down for the pairs that are difficult to split. This is a happy coincidence. After all, if we could accurately predict whether or not a challenging pair can be split under every conceivable circumstance, then there would be little point in going out to the telescope to try. For the challenging pairs the very point of observing them is to try to push your limits, not knowing if you are going to be successful. If our predictive algorithm says a pair is going to be very difficult to split, sure, it may not be perfectly accurate. In truth the pair may be easier than predicted, or it may not be splittable at all. But if used correctly, the algorithm can still predict which pairs are challenging, regardless of whether or not the detailed prediction is accurate.



ok, the predictive algorithms break down exactly where they are needed most. you must see here that the problem is not with the algorithms but with your use of the term "predictive", which merely begs the question and muddles the issue. any categorization runs up against problematic cases, where one must shrug and toss the case into one category or another. the case isn't difficult to predict, it's difficult to categorize or sort. and categorization, as we all know, is just a shorthand form of description. creating a new category that you call "challenging" doesn't change the basic procedure.

what seems beguiling to the layperson is the ritualistic method by which the "predictive model" is developed. you're only creating a database sorting rule. yes, it's a "consensus" database sorting rule, because you have a lot of individual observers "voting" as to which stars shall be classified this or that way by it. but one could (as i have) create a purely theoretical or judgmental sorting algorithm to combine aperture, magnitude, etc. into a double star "difficulty score", and it amounts to exactly the same thing -- "challenging" pairs can be identified, which are usually either "unsplittable" or "easy". as long as everything stays in a database, nothing is "predicted".

if the goal is to identify, as you say, stars that will be easy or difficult given the instrument and conditions, then i'll just assert that most experienced observers already do that with pretty rudimentary, rough guess rules based on magnitude, magnitude limit and separation, given personal experience with their instrument and observing conditions. since a "challenging" pair is likely to turn out "unsplittable" or "easy" anyway, nothing more elaborate seems useful.

the fundamental question is simple: what makes a double star "difficult"? the magnitude difference by itself is meaningless, because on the one hand the primary can be so bright that it produces substantial glare or scatter, and on the other hand the primary can be so faint that the companion is pushed below the visual limit. simply articulating that explanation of why a pair *may be* difficult seems to me far more valuable than using those factors to "predict" that the pair *will be* difficult. the explanation nurtures an observer's skill, while the ritual of pseudoprediction just paves a new landscape of boredom.

it's not a "happy coincidence" that your descriptive models break down when put to the task of prediction rather than sorting data: it's an outcome that any psychometrician can predict will occur, with a high probability of being right.


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blb
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Reged: 11/25/05

Loc: Piedmont NC
Re: Research project - Limit for uneven Double Stars new [Re: drollere]
      #5443742 - 09/27/12 03:51 PM

Quote:

Quote:

The pedants always say the same thing: there is no way you can do that accurately, particularly for things near the limits. And they are right! But here's the thing: just being in the ballpark is enormously useful in real world applications. ...



well, as one of those "pedants" i'm happy to concur with your agreement that "we" (i) are correct in our skepticism. however, you seem to concede a point while denying it, as prediction that doesn't work is still "enormously useful", which leaves me unclear as to what you want to say.




Well I am one of those that thinks that if enough people will try to make the observations on enough nights, that there will probably be enough observations with good conditions, that the formula will be a good predictor and with good optics and looking on enough nights that you will split it to, if the formula says it is possible. In other words we need as many observers as possible and fewer nay sayers


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blb
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Reged: 11/25/05

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Re: Research project - Limit for uneven Double Stars new [Re: blb]
      #5443756 - 09/27/12 04:06 PM

Quote:

really? if you only date those few persons that you "predict" will give you a good night kiss, then you've taken a hell of a lot of excitement and adventure out of dating; and similarly if you only look for double stars that you "predict" in advance will be "kissing", then you've merely fallen into a more elaborate and ritualistic form of routine, and you have not really addressed what seems to be your complaint, which is that the observer should challenge himself with something genuinely novel or unknown. you've just replaced a rut of consensus with a rut of "prediction", which seems to mean a consensus as to how doubles look without actually looking at them. at least, looking was how those lists you disparage were compiled.

the crux is that you seem embarked on the project of telling me what i will see before i've actually looked at it, rather than telling me why something may be difficult to perceive when i try to look for it, which is a very different type of guidance.




Really, with only the difference in magnitude at a limit of only 4, I think that there are still many stars to challenge us. When planning a nights observing I like the idea of knowing, if the sky cooroporates, I have a chance of seeing an object. If the formula works properly, we will be hunting those nights with good observing conditions and not hunting for something we do not have a chance to see. I see this as something that will tell me if this is an object that if I have good optics, observing conditions, etc., it will or will not be worth spending my time on. We all do this mentaly anyway based on our experences observing.


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drollere
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Reged: 02/02/10

Loc: sebastopol, california
Re: Research project - Limit for uneven Double Stars new [Re: blb]
      #5446709 - 09/29/12 12:19 PM

well, i'm trying to be constructive and not rain on the parade. there's a lot to be learned for all involved by the exercise of looking for a better rule than is already out there. based on long experience collecting and analyzing performance and attitude data, and observing the way this parade is conceived ... the parade is the thing, not the prediction.

a point i omitted before that is crucial: the database itself is corrupt. not the observer data, but the WDS data that you want to use as your basis for "prediction". please skim the topic here on jonckheere doubles, and see what you conclude.

greg made the point that a rule that actually doesn't reliably "predict" anything is still useful to entice you to *look at* something -- as buddy says, to tell the observer in advance that something "is worth spending my time on." but a blindly applied *categorization rule* can't tell you that, only a consensus of observers can tell you that. you're pretending a rule leads you somewhere that you wouldn't go on your own. that to me is the crux.

everyone can make a pretty good guess about what is "worth looking at" using only primary magnitude, magnitude difference, binary separation and telescope aperture -- they just need to form an expectation, look, and then think for a minute about why their expectation was or was not met. in my obstreperous opinion, that is both a faster way to develop your observing skills, and a more rewarding form of observing.

but ... this is a hobby of diff'rent strokes, and good on us all.


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stray1
sage


Reged: 09/03/12

Loc: SW Ohio
Re: Research project - Limit for uneven Double Stars new [Re: drollere]
      #5495707 - 10/30/12 02:32 AM

I'm in.

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cphk96
member


Reged: 11/01/07

Loc: North Hollywood, CA
Re: Research project - Limit for uneven Double Stars new [Re: stray1]
      #5499179 - 11/01/12 10:40 AM

I want to take part in this project.

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azure1961p
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Reged: 01/17/09

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Re: Research project - Limit for uneven Double Stars new [Re: FrenchStar]
      #5501484 - 11/02/12 07:56 PM

Quote:

I invite you all to read the September 2012 issue of Sky and Telescope(It's at page 68).

Sissy Haas is asking our help to complete a very interesting project. I invite you all to participate!




Well that's a nice invite but really, if its that important to her and these results through this forum could be that valuable why are you sitting in for her with the request? Wouldn't it serve her interests to get involved here like you.



Pete


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Cotts
Just Wondering
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Reged: 10/10/05

Loc: Toronto, Ontario
Re: Research project - Limit for uneven Double Stars new [Re: azure1961p]
      #5505121 - 11/05/12 09:17 AM

Whether Ms. Haas is a member here or posts here or not is irrelevant. It has come to the attention of many of us (through this thread or via S&T) that she is requesting help and some of us are volunteering to do so.

Dave

Edited by Cotts (11/05/12 09:19 AM)


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