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Astronomical data by James Randi - Fri, 29 Jun 2018 13:36:57 EST ID:BPHCgbLm No.57327 Ignore Report Quick Reply
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I had an idea to build a digital astronomical clock for fun in unity as a learning exercise. It would include solar system clock showing the "time" and such on various planets and a 3rd model of the solar system.
I'd like to try aim for a bit of realism and have the models of planets be in accurate locations to real life.
What would be the best source for finding out planet locations so that they don't all start in the 12 oclock position when I start my program?
Like if I added Mars, how do I find how far into its solar year (month?) It currently is on Mars?

I'm new to coding in general, I already have the data for earth but that's done simply by telling the program to check the system clock and moves the model of earth to right orientation.
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Fred Hoyle - Sat, 30 Jun 2018 17:15:53 EST ID:457vC2+I No.57330 Ignore Report Quick Reply
>>57327
I think the simplest thing to do would be for you to study orrery tables. You're basically constructing a digital orrery, so you'll need to know more than just where the planets are now, you need to accurately model their rate of motion and the elipticalness of their orbits if you want things like the retrograde motion of Mars to work properly.

If I were coding it, first I would get the model producing accurate planet locations in a simple 2D view, then export the planar location data back to the 3d environment. That way you can tackle each problem individually. Post it up if you finish.
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James Randi - Sat, 30 Jun 2018 20:16:53 EST ID:lAN8qbQT No.57331 Ignore Report Quick Reply
>>57330
You can just google the rate of motion, thats not the issue. I didn't think about the elliptical orbits.

This is literally the first program im ever writing on my own so it will take some time.
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James Randi - Sun, 01 Jul 2018 06:49:38 EST ID:lAN8qbQT No.57332 Ignore Report Quick Reply
I did some digging. I couldn't find any tables for oerrys but I did find several 3d models for real ones for 3d printing and CNC machines. I guess I could just render one in unity and run a physics simulation on it and call it a day.
I know this isnt the programing board but what do you guys think?
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Georges-Henri Lemaitre - Wed, 04 Jul 2018 11:00:52 EST ID:IRQpyxVi No.57335 Ignore Report Quick Reply
>>57327
This is going to be a massive undertaking if you really plan on including what time it is on every planet. For one thing, what determines the "12" position on Earth is the position of the sun and moon in the sky during particular times of day, likely with the baseline established by its position being viewed from the Equator..

12 pm could be chosen to represent when the sun is 3/7ths across the sky if we wanted to, not to mention the fact what time it is here on Earth depends on which time zone you're in, and the boundaries between one time zone and the next are mostly arbitrary. are you going to create time zones for all the other planets? how are you going to decide how many and where to divide one from the next?
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Georges-Henri Lemaitre - Wed, 04 Jul 2018 11:18:07 EST ID:IRQpyxVi No.57336 Ignore Report Quick Reply
>>57335
fuck, i cut out parts of the post i didnt mean to and left a part i didn't want left in because i was gonna make a suggestion for doing something and realized id rather leave it out since it didnt seem to go with what you had in mind.

what i was trying to let you know is, though, that finding out what time it is on other planets is that you're going to have to look up how the time of day was initially decided on being determined for each respective time-zone on Earth. Along with that, since the boundaries for time-zones are mostly arbitrary, but aren't entirely, you're going to have to look up the criteria that was used for ultimately deciding where a boundary would be placed by those that established GMT. Then you're going to have to do a little of analysis and decide how to best place those boundaries on each individual planet with respect to its size, its distance from the sun, the shape of its orbit and how variable its distance from the sun potentially is during a given time of year in its orbit, the rate it makes a full revolution in its planetary spin, etc.

It's gong to require some serious effort even without including the programming. Hope things turn out well for you, just don't mistake that it'll be a lot of time and work.
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James Randi - Thu, 05 Jul 2018 17:55:01 EST ID:CxvjOUYt No.57338 Ignore Report Quick Reply
>>57336
Well I geuss I'd have to give each planet its own calender's then.
fun project.
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James Randi - Fri, 06 Jul 2018 20:46:11 EST ID:CxvjOUYt No.57340 Ignore Report Quick Reply
any links to some sort of table would be helpful too
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Urbain Le Verrier - Sat, 21 Jul 2018 13:39:49 EST ID:hGyQlc1t No.57355 Ignore Report Quick Reply
>>57340
https://ask.metafilter.com/86383/Where-can-I-find-data-on-planetary-positions-and-velocities
they mention:
https://ssd.jpl.nasa.gov/?horizons#elem
digging a little there is also this:
https://github.com/mommermi/callhorizons
which leads to this
https://www.google.com/search?q=Astroquery
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Urbain Le Verrier - Sat, 21 Jul 2018 13:51:43 EST ID:hGyQlc1t No.57356 Ignore Report Quick Reply
>>57340
Digging a little lets me realize that using that python api would be massive overkill
The table you want is here:
https://ssd.jpl.nasa.gov/?planet_pos
or to precise in this pdf document:
https://ssd.jpl.nasa.gov/txt/aprx_pos_planets.pdf


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