APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Comments and questions about the APOD on the main view screen.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by skyhound » Tue Jun 28, 2016 11:08 pm

Am I the only one who looks at renderings of Jupiter like this and thinks, "Wrong, wrong, wrong?" (measures Jupiter on screen both ways) Jupiter is not a sphere. It is flattened at the poles to a numerically small, but distinguishable degree. When you consider the calculations that go into making an animation like this to appear accurate, I'll never understand why so few take the time to get the oblateness right. It does make it easy to discern a simulation from the real thing though, at least for me.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by geckzilla » Tue Jun 28, 2016 11:12 pm

skyhound wrote:Am I the only one who looks at renderings of Jupiter like this and thinks, "Wrong, wrong, wrong?" (measures Jupiter on screen both ways) Jupiter is not a sphere. It is flattened at the poles to a numerically small, but distinguishable degree. When you consider the calculations that go into making an animation like this to appear accurate accurate, I'll never understand why so few take the time to get the oblateness right. It does make it easy to discern a simulation from the real thing though, at least for me.
You are not alone. This pet peeve doesn't pertain to this APOD at all, but yeah. I think to myself, come on, how hard is it to add a little flattening to that sphere you just created? Not hard at all. Here you go, have some planets I rendered a while back.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by Chris Peterson » Tue Jun 28, 2016 11:26 pm

geckzilla wrote:
skyhound wrote:Am I the only one who looks at renderings of Jupiter like this and thinks, "Wrong, wrong, wrong?" (measures Jupiter on screen both ways) Jupiter is not a sphere. It is flattened at the poles to a numerically small, but distinguishable degree. When you consider the calculations that go into making an animation like this to appear accurate accurate, I'll never understand why so few take the time to get the oblateness right. It does make it easy to discern a simulation from the real thing though, at least for me.
You are not alone. This pet peeve doesn't pertain to this APOD at all, but yeah. I think to myself, come on, how hard is it to add a little flattening to that sphere you just created? Not hard at all. Here you go, have some planets I rendered a while back.
Try rendering with different viewing distances, and note the point where you can no longer tell that the planets are oblate.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by geckzilla » Wed Jun 29, 2016 1:02 am

Chris Peterson wrote:
geckzilla wrote:
skyhound wrote:Am I the only one who looks at renderings of Jupiter like this and thinks, "Wrong, wrong, wrong?" (measures Jupiter on screen both ways) Jupiter is not a sphere. It is flattened at the poles to a numerically small, but distinguishable degree. When you consider the calculations that go into making an animation like this to appear accurate accurate, I'll never understand why so few take the time to get the oblateness right. It does make it easy to discern a simulation from the real thing though, at least for me.
You are not alone. This pet peeve doesn't pertain to this APOD at all, but yeah. I think to myself, come on, how hard is it to add a little flattening to that sphere you just created? Not hard at all. Here you go, have some planets I rendered a while back.
Try rendering with different viewing distances, and note the point where you can no longer tell that the planets are oblate.
I dunno, when viewed face on, it has to go pretty far. Down until the difference is less than a pixel and even then you could tell if you zoomed in close enough and added up the brightness of each pixel. I guess the higher (or lower) the inclination it's being viewed from, the less obvious it would be.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by Chris Peterson » Wed Jun 29, 2016 1:18 am

geckzilla wrote:
Chris Peterson wrote:Try rendering with different viewing distances, and note the point where you can no longer tell that the planets are oblate.
I dunno, when viewed face on, it has to go pretty far. Down until the difference is less than a pixel and even then you could tell if you zoomed in close enough and added up the brightness of each pixel. I guess the higher (or lower) the inclination it's being viewed from, the less obvious it would be.
Wrong direction. How close do you need to get before you can't detect the oblateness? A lot of the NASA renderings are views from orbit, where you see much less than a hemisphere, and that will result in a circular projection.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by geckzilla » Wed Jun 29, 2016 1:37 am

Chris Peterson wrote:
geckzilla wrote:
Chris Peterson wrote:Try rendering with different viewing distances, and note the point where you can no longer tell that the planets are oblate.
I dunno, when viewed face on, it has to go pretty far. Down until the difference is less than a pixel and even then you could tell if you zoomed in close enough and added up the brightness of each pixel. I guess the higher (or lower) the inclination it's being viewed from, the less obvious it would be.
Wrong direction. How close do you need to get before you can't detect the oblateness? A lot of the NASA renderings are views from orbit, where you see much less than a hemisphere, and that will result in a circular projection.
Oh, heh. That doesn't really have anything to do with my (and presumably skyhound's) gripe. Another thing that can hide the oblateness is when the planet is in a gibbous phase. I've only ever noticed it when the whole planet is in view and fully illuminated. There are an awful lot of videos and plain images with spherical Jupiters and Saturns when you start looking. It bothers me because it seems profoundly lazy to not add one small change to the geometry so you don't end up with a perfect sphere.

A recent example.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by skyhound » Wed Jun 29, 2016 5:46 am

I have to apologize for somehow posting my comment to the wrong APOD. I meant it for the Juno Mission Trailer on June 28. Chris, I have rendered Jupiter from many different distances and perspectives, and you'd have to go to extremes for the lack of obtateness not to be obvious once you learn to look for it. In fact, when I see Jupiter rendered as a sphere I experience an interesting psychological effect. I am so used to the oblateness that when I see Jupiter drawn without it, it appears elongated in the North/South direction, like an egg standing on end. Why is it stretched? That's usually when I get my ruler out. :-) I think perhaps the difference is in what people are used to looking at. Those who spend a lot of time at the telescope or looking at photographs have come to expect the oblateness. This isn't necessarily true of the people creating the animations. I suspect many viewers have a nagging feeling that something isn't quite right, but can't put their finger on it.
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by skyhound » Wed Jun 29, 2016 8:59 pm

So I just found this NASA App that displays Juno in real time, which is cool. As a bonus, Jupiter is rendered with the proper shape.

https://eyes.nasa.gov/eyes-on-juno.html
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Re: APOD: Jupiter's Clouds from New Horizons (2016 Jun 26)

Post by tennisjazz » Thu Jun 30, 2016 5:05 am

the link (to http://pluto.jhuapl.edu/mission/whereis_nh.php) at successfully complete its main flyby of Pluto is broken