To compute refraction for objects below horizon, simply add ABS (absolute value) for each altitude, in the calculus for refraction. For example 8 degrees ALT , gives 8.1 degrees apparent. Then, -8 degrees Alt, would give -8.1 degrees ALT.
As to why it would be useless in practice. Sometimes you need to consider that you don't always know everything about everything, even if your are an exceptional programmer and Human being.
I've seen Sellarium be usefull for a great variety of professions. It would me very usefull for many people, trust me.
Relax.
Thanks
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Refraction is not really defined below an altitude of minus 3 or minus 4
degrees. I know that the formula
can go to -90 but that is bogus (just read the conditions for the formula
carefully).
So IMHO it is not really possible (scientifically) to provide refraction
below -3 or -4 degrees.Perhaps people would like to see it, but there is no
real proper simple formula for it... Also the variability of refraction
becomes very high below -2 degrees.
See some evaluation: http://www.archaeocosmology.org/eng/refract.htm
To compute refraction for objects below horizon, simply add ABS (absolute
value) for each altitude, in the calculus for refraction. For example 8
degrees ALT , gives 8.1 degrees apparent. Then, -8 degrees Alt, would give
-8.1 degrees ALT.
As to why it would be useless in practice. Sometimes you need to consider
that you don't always know everything about everything, even if your are an
exceptional programmer and Human being.
I've seen Sellarium be usefull for a great variety of professions. It
would me very usefull for many people, trust me.
To compute refraction for objects below horizon, simply add ABS (absolute
value) for each altitude, in the calculus for refraction. For example 8
degrees ALT , gives 8.1 degrees apparent. Then, -8 degrees Alt, would give
-8.1 degrees ALT.
This is totally wrong thinking. Refraction is not that simple!!!!
Please check the link I gave earlier.
Again refraction below some 4 degrees is not really known (or one needs an
implementation of a quite complex model: like Hohenkerk did [see again my
above link]). But for normal use (aka on the earth surface) refraction upto
4 degrees is really the max to predict/calculate.
There are things in science/life that are not yet easy to calculate with a
normal computer;-)
All the best,
Victor
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The formula currently used has a division by zero somewhere a few degrees below the horizon. Therefore we must disable refraction around -2 degrees, and we cannot go to -90 in a smooth mirroring effect (which I still find totally useless in the first place). I see no application for this, unless you can describe properly what would be the added benefit, and where one could find application for a model that describes what you sketched above. Simulating e.g. high-altitude ballooning would require a totally different model. As Victor pointed out, even refraction close to the horizon can become much more complicated in real-world scenarios.
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Well, the benefict is in real world applications. For example, did you know that even under 10º or 20º the sun might have an impact on you? That means the world is a shpere and globalization indicates that those guys (a few miles away from horizon) will afect your existence, ruled by 10º plus 0,1.
Apparent ALT would be calculated from relgular abs(ALT). And on the extremes, you would place a max(abs(alt(degrees();abs(alt(degreesbelow))). Might need a * sign.
Hope you get it.
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Allright, so if you want it absolutelly scientific then why do you need it to
show negative altitudes?????????????
ummm... if an object is up to -4 degrees below the horizon, atmospheric
refraction can easily make it appear to be above the horizon... whether this
object is a planet, star, or satellite the appearance of being above the horizon
is real in real life...
Stellarium is INFORMATIVE, not REPRESENTATIVE of the real universe.
that may be and if it is true, should it not reflect that when i see an object
hovering above the horizon and look to see what it is, that i am informed of
what that object really is instead of seeing nothing there in stellarium?
2cents, FWTW...
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I'm not suggesting taking off refraction calculations. I'm suggesting adding an exta button, so that it is possible to compare the above horizon objects with under horizon objects, for the same conditions.
Right now, it's almost impossible to evaluate this because of sun glare to the whole scene. And if if you evaluate altitude of objects with refraction turned on, you will get two diferent numbers for the same geometric positions.
For the same reason I recommend this, is because ALL objects are magnified by atmosphere. Under horizon objects are no different that others.
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Can't you disable/enable atmosphere to see difference of coordinates? A couple years ago users asked us remove an additional Alt/Az lines from infobox (yes, "very many info" is reason of the requests).
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Alexander, yes I can. It's small, but it be decisive.
It would need (of course) a checkbox not on the Configurantion menu / Information, but it could be on Sky / Atmosphere.
That is because the extra line would appear always when the atmosphere checkbox "dual refraction" is checked. The explanation for that checkbox could be: "When active, refraction is calculated for all objects".
I suggest that the regular line to be maintained, and that the second (optional) line is almost identical at high altitudes (except signal), and only differ at low altitudes, for the same non corrected value.
Thanks
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Sorry, I made a mistake on the last post. When you read:
I suggest that the regular line to be maintained, and that the second (optional) line is almost identical at high altitudes (except signal), and only differ at low altitudes, for the same non corrected value.
It should be:
I suggest that the regular line to be maintained, and that the second (optional) line values are the same for same non corrected values (except signals).
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We apply refraction where it makes sense and where there is a model available in the literature. We are fully aware that this model is incomplete with respect to lower atmosphere layering conditions which can occur in a real-world scenario (inversion, Novaja Semliya effect,...). Analytic models are available in the physics literature for refraction model conditions for standard atmosphere and observers on the ground, and provide values applicable downto the mathematical horizon, at best. We already stretch this to somewhat below horizon to provide consistent images for high-mountain views.
We do not apply refraction where there is not a meaningful model and where it does not make sense to do so. Objects under the horizon cannot be observed.
It is meaningful to give a geometric altitude for objects below the mathematical horizon, but it is not meaningful to invent some faked (shall I say, "alternative"?) refraction value just to fill the screen with numbers for applications by some particular anonymous user group.
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Hello,
I would recomend a new button under the athmosphere menu. That is, it should be possible to:
Thanks
Great software!!!!!!!!!!!!!!!!!!!!!!!!!!
And how do you compute refraction for objects below horizon? There is no such model as this is totally useless in practice.
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Hello,
To compute refraction for objects below horizon, simply add ABS (absolute value) for each altitude, in the calculus for refraction. For example 8 degrees ALT , gives 8.1 degrees apparent. Then, -8 degrees Alt, would give -8.1 degrees ALT.
As to why it would be useless in practice. Sometimes you need to consider that you don't always know everything about everything, even if your are an exceptional programmer and Human being.
I've seen Sellarium be usefull for a great variety of professions. It would me very usefull for many people, trust me.
Relax.
Refraction is not really defined below an altitude of minus 3 or minus 4
degrees. I know that the formula
can go to -90 but that is bogus (just read the conditions for the formula
carefully).
So IMHO it is not really possible (scientifically) to provide refraction
below -3 or -4 degrees.Perhaps people would like to see it, but there is no
real proper simple formula for it... Also the variability of refraction
becomes very high below -2 degrees.
See some evaluation: http://www.archaeocosmology.org/eng/refract.htm
All the best,
Victor
On 9 February 2017 at 02:06, noreply@in.sf.net wrote:
On 9 February 2017 at 02:06, noreply@in.sf.net wrote:
This is totally wrong thinking. Refraction is not that simple!!!!
Please check the link I gave earlier.
Again refraction below some 4 degrees is not really known (or one needs an
implementation of a quite complex model: like Hohenkerk did [see again my
above link]). But for normal use (aka on the earth surface) refraction upto
4 degrees is really the max to predict/calculate.
There are things in science/life that are not yet easy to calculate with a
normal computer;-)
All the best,
Victor
The formula currently used has a division by zero somewhere a few degrees below the horizon. Therefore we must disable refraction around -2 degrees, and we cannot go to -90 in a smooth mirroring effect (which I still find totally useless in the first place). I see no application for this, unless you can describe properly what would be the added benefit, and where one could find application for a model that describes what you sketched above. Simulating e.g. high-altitude ballooning would require a totally different model. As Victor pointed out, even refraction close to the horizon can become much more complicated in real-world scenarios.
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Well, the benefict is in real world applications. For example, did you know that even under 10º or 20º the sun might have an impact on you? That means the world is a shpere and globalization indicates that those guys (a few miles away from horizon) will afect your existence, ruled by 10º plus 0,1.
Apparent ALT would be calculated from relgular abs(ALT). And on the extremes, you would place a max(abs(alt(degrees();abs(alt(degreesbelow))). Might need a * sign.
Hope you get it.
No.
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"No", for what?
No, I don't get it.
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This is starting to sound religious... Stellarium is a scientific software.
Right. This is about atmospheric refraction, not globalization and affection of existence.
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Allright, so if you want it absolutelly scientific then why do you need it to show negative altitudes?????????????
Stellarium is INFORMATIVE, not REPRESENTATIVE of the real universe.
See ya!
On 02/09/2017 05:22 PM, noreply@in.sf.net wrote:
ummm... if an object is up to -4 degrees below the horizon, atmospheric
refraction can easily make it appear to be above the horizon... whether this
object is a planet, star, or satellite the appearance of being above the horizon
is real in real life...
that may be and if it is true, should it not reflect that when i see an object
hovering above the horizon and look to see what it is, that i am informed of
what that object really is instead of seeing nothing there in stellarium?
2cents, FWTW...
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Hello,
I'm not suggesting taking off refraction calculations. I'm suggesting adding an exta button, so that it is possible to compare the above horizon objects with under horizon objects, for the same conditions.
Right now, it's almost impossible to evaluate this because of sun glare to the whole scene. And if if you evaluate altitude of objects with refraction turned on, you will get two diferent numbers for the same geometric positions.
For the same reason I recommend this, is because ALL objects are magnified by atmosphere. Under horizon objects are no different that others.
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I suppose this would be a non-graphical proposition. But it needs a second (Az/Alt apparent) line.
Can't you disable/enable atmosphere to see difference of coordinates? A couple years ago users asked us remove an additional Alt/Az lines from infobox (yes, "very many info" is reason of the requests).
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Alexander, yes I can. It's small, but it be decisive.
It would need (of course) a checkbox not on the Configurantion menu / Information, but it could be on Sky / Atmosphere.
That is because the extra line would appear always when the atmosphere checkbox "dual refraction" is checked. The explanation for that checkbox could be: "When active, refraction is calculated for all objects".
I suggest that the regular line to be maintained, and that the second (optional) line is almost identical at high altitudes (except signal), and only differ at low altitudes, for the same non corrected value.
Thanks
It looks as though you mock us. Why are you trying so hard to complicate things?
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Sorry, I made a mistake on the last post. When you read:
I suggest that the regular line to be maintained, and that the second (optional) line is almost identical at high altitudes (except signal), and only differ at low altitudes, for the same non corrected value.
It should be:
I suggest that the regular line to be maintained, and that the second (optional) line values are the same for same non corrected values (except signals).
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Alexander, the reason I'm doing this proposition is because I know I represent a particular group of people that use stellarium in this way.
It also seems techically simple.
More details please.
Are you want always apply refraction?
We apply refraction where it makes sense and where there is a model available in the literature. We are fully aware that this model is incomplete with respect to lower atmosphere layering conditions which can occur in a real-world scenario (inversion, Novaja Semliya effect,...). Analytic models are available in the physics literature for refraction model conditions for standard atmosphere and observers on the ground, and provide values applicable downto the mathematical horizon, at best. We already stretch this to somewhat below horizon to provide consistent images for high-mountain views.
We do not apply refraction where there is not a meaningful model and where it does not make sense to do so. Objects under the horizon cannot be observed.
It is meaningful to give a geometric altitude for objects below the mathematical horizon, but it is not meaningful to invent some faked (shall I say, "alternative"?) refraction value just to fill the screen with numbers for applications by some particular anonymous user group.
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Alexander:
High-End Astrologers.
Thanks
It's fully explains