algorithm

[sayehu]

What algorithms does Stellarium use to support its accuracy for observing constellations?

[Georg Zotti]

Those mentioned in the User Guide and source code. What accuracy do you need to observe constellations?

[sayehu]

Accuracy in finding coordinate points at a particular place of a constellation.

[Hans]

You mean like how interpolation is done ?

[sayehu]

Yes, that's right, like how the interpolation is done in the constellations? This has prompted my curiosity, because Stellarium is the only open surce planetarium that is widely used by amateur sky object observers and even professionals.

[Hugo]

Is the question how Stellarium measures "place and speed" of individual objects in the database or is the question, how does the measured observation subsequently come into the software?

[sayehu]

how does Stellarium measure the "place and speed" of certain constellation objects? and how is the measured accuracy of observation (constellation) entered into the software?

[Georg Zotti]

Stellarium does not measure anything. It simulates the solar system using mathematical methods and physical models devised over the past 2400 years or so.

The sources of our wisdom are given in the User Guide. The algorithms are in the referred works, and implementation is visible in the open source code.

There are other open and closed source programs used by amateur and professional astronomers. Each has its special strengths and weaknesses. You have the freedom of choice to use what you like best.

I don't understand your question about "interpolation of a constellation". What is your definition of "constellation"?

[sayehu]

Good, thank you for your answer I am very satisfied with the answer. And indeed, I do not mean to ask Stelllarium measurements of the constellations for example. but I just want to know how to calculate the constellations so that they are recognized precisely their existence.

[Hugo]

Hm, constellations are not calculated, they are observed and measured. (On December 3, 2020 the first part of the third Gaia star catalog was published.) Only the mechanics of the tracking as part of the mount ensure that each set celestial object remains exactly in the center of the field of view of the telescope or camera. - The precision is the same everywhere, inside and outside the constellations. 

[Wolfgang Laun]

There's a lot of calculation required if, given the geocentric coordinates of a star in some catalog, you want to have the coordinates of the star on Stellarium's display. The star catalog uses a certain coordinate system and a certain epoch. Computation is required to shift the coordinate to Stellarium's date and time. If we require high precision (and the difference in time is big) the effect of the star's proper movement may have to be considered. Then, unless Stellarium is set to geocentric coordinates, a transformation to topocentric coordinates is required. Unless the effects of the atmosphere have been turned off, the displacement due to atmospheric refraction must be computed. But you still have coordinates in a spherical coordinate system (which is fine for pointing your telescope) but is useless until they come up with a computer display shaped like a hemisphere or quarter sphere. (Let's ignore planetariums for this discussion, OK?) You'll have to find a mapping of the section of the spherical sky that should be shown on your display, and you'll need some good map projection for the mapping of sphere to plane. What is "good" depends on a lot of parameters, but you won't be able to use the same projection all of the time...

There would be even more if we are requiring extreme precision, but I think that this is enough. I have found Jean Meeus' book Astronomical Algorithms a helpful source for all the required formulas. (It doesn't elaborate much on the derivation of those formulas.)

Wolfgang

 

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Wolfgang Laun

[Hugo]

A geometer as long as a point does not contribute to a better understanding. The complexity of mathematics increases as astrophysics seeks explanations for observations or as unproven mathematical theorems are used in experimental astronomical research. When it comes to achieving high accuracy in a certain constellation, as many well-known mathematical theories as astrophysics have produced them will be used. What is already implemented in Stellarium was mentioned in the User Guide and source code. It can only be explained more precisely if the question names its specific constellation and someone familiar with the source code comments on it.