Orrery (Earth, Moon, and Sun) | Hacker News Reader

Orrery (Earth, Moon, and Sun)

instructables.com

96 pointspmontra13 comments

I don't get how one can get realistic modeling of eclipses without taking into account the eccentricity of Earth's orbit around the Sun (it not only minorly affects the distance, but more imporantly it causes the angular speed of Earth around the Sun to vary).

Am I overestimating the impact of that error, missing a description of how it was accounted for, or something else?

You might be able to compensate for that in the calendar track?

My intuition is that that would affect the location of the eclipse track across the earth, but that it’s not enough to significantly shift the date of the eclipse since that’s more determined by the moon’s location.

Isn't the earth's eccentricity incredibly low? (To the point that human-noticeability or non-precision-machinability are out of the question?)

That's not to say I have any comment on the accuracy of ellipse calculation. Keplerian mechanics are beyond me. But I did see a the gear-ratio calculation repo linked: https://github.com/amandaghassaei/tellurion-orrery/tree/main...

It seems angular positional error after 100 years of simulation was the optimization goal.

> Isn't the earth's eccentricity incredibly low? (To the point that human-noticeability or non-precision-machinability are out of the question?)

It's one-percentish, and causes the length of time between equinoxes to be shorter on the northern-hemisphere-winter-side by a day or so. The date scale on the model includes single-day divisions, which made me think that such accuracy was intended; perhaps I was wrong in that.

Amazing. Well done!

I can't do all that mechanical engineering, CNC cutting etc.; I'm not meticulous and careful enough to manufacture the parts. But if someone offered a kit of finished (metal) parts, I'd be up for buying two (subject to price, of course).

Not your standard instructables, I must say. I don't think there are too many people that have the right skill set and access to the tools and materials required to build this, however. Amazing work.

It seems like you could 3D print all of it

Plastic doesn't really have the same feel to it, does it? I think the project shows great craftmanship, which 3D printing simply does not.

Brass of course looks fancier, but in terms of craftsmanship I don't know if there is such great gulf between cnc milling and 3d printing, both are processes where the computer does the physical part of the process

After watching clickspring on YouTube I think it is clear that you need very few tools to make something like this, just knowledge, skill and ingenuity!

Just last week I visited Eise Eisinga’s planetarium in Franeker, The Netherlands (https://www.planetarium-friesland.nl/en/). Finished in 1781, he used only wood and nails to fit an intricate and quite accurate orrery in the ceiling of his fairly modest house. This Instructable is very enticing!

Is there a 3rd printer model available?

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