Not really a macro

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soldevilla
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Not really a macro

Post by soldevilla »

exactly. It's not a macro, but after hours of staring at the screen to try and see a stereo pair, maybe it's nice to have other points of view :)

Yesterday the sky was especially stable and allowed me to take more detailed images than is normal in my observatory. I have mounted a stereo pair with two images slightly separated in time. I hope you can forgive me for the off topic, just once
Attachments
stereo.jpg

rjlittlefield
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Re: Not really a macro

Post by rjlittlefield »

Interesting! Well, we talk a lot about stereo, so it's on topic in that respect. :) But we may want to move this topic to Technical Discussions at some point.

This stereo pair works pretty well for me, but there are a few opportunities for improvement.

First is that it's laid out for parallel viewing, not this forum's usual crossed-eye layout. When viewed with crossed eyes, the depth inverts and the planet looks like the hollow inside of a hemisphere, with the moon seen a little behind the edge like a "transparent foreground" artifact.

Second is that the unmatched bright spot at lower right (another moon?) introduces for me a sort of distracting flashing or flickering effect. I know what causes that effect, so I can consciously ignore it. But less practiced viewers may find it troubling and not know why.

Third is that the axis of rotation is tipped about 17 degrees with respect to the horizontal axis of layout. This means there is a small amount of vertical disparity that will degrade stereo lockup for some viewers.

I can post a version with these issues addressed, if you like.

--Rik

soldevilla
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Re: Not really a macro

Post by soldevilla »

Of course, you can play as you want.
But there are a reason for that:🤣

I use a chinese glasses for to watch stereo (parallel) pairs, the only way for me for to watch them.

The second satelit exit from the shadow of Jupiter between the two photos 🤷‍♂️.

I need to put the planet in order the movement of the planet in the sky be parallel to the axis of the telescope mount.

Happy if you modify it in order more people can enjoy with jupiter in volume 👍

rjlittlefield
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Re: Not really a macro

Post by rjlittlefield »

It is one of my favorite sayings: "There are tradeoffs..."

What I have done here is to eliminate the 2nd moon which could not participate in the stereo, and I have rotated the images so that the axis of rotation is horizontal or almost so, and I have made layouts for both parallel and crossed eye viewers.

Crossed:

Image


Parallel:

Image


I hope this helps!

--Rik

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Re: Not really a macro

Post by rjlittlefield »

By the way, which moon is this?

--Rik

soldevilla
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Re: Not really a macro

Post by soldevilla »

the big one, in the edge, is Ganymede. The "white" dot over the planet is Europa and the erased :smt089 one was Io

Troels
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Re: Not really a macro

Post by Troels »

Very interesting exercise. And it certainly looks as if there is some depth in the picture (the new cross viewing version).

Since there is no visual paralaxe between the two pictures, just a time difference, the depth illusion must be created by the rotation of Jupiter as well as the circular movement of the moons. It is thus very convenient that these rotations has the same direction. But if the angular speed of a moon is different from an other moon or the angular speed of the surface of Jupiter this difference must create unrealistic perceptions.
If I understand it correctly a higher angular velocity (measured in degrees from the center of Jupiter) would make a moon look closer to the observer relative to Jupiter because of the greater lateral difference between the two positions of the moon in the pictures.

Jupiter has a suprisingly fast rotation: a little less than 10 hours per rotation.
Europa has an orbital period (a Io-year) of just 3.55 (earth-)days or around 85 hours.
And Ganymedes uses 7.15 days or around 170 hours.

If my understanding is correct the fast moving Europa should look closer to us than the slower Ganymedes. It is difficult to see.
Also the roundness of Jupiter should be more pronounced?
Perhaps it is all just a result of a short time between the pictures apparently compressing all the distances along the line of view?

According to the numbers Europa should keep a distance to Jupiter of around 5 times Jupiters diameter and Ganymedes circles at a distance of 7 Jupiter diameters. I am not sure my eyes would be able to focus at a stereogram with such realistic proportions!
Your take might be the best compromise between realism and usability.
Thanks for sharing!
Troels Holm, biologist (retired), environmentalist, amateur photographer.
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rjlittlefield
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Re: Not really a macro

Post by rjlittlefield »

Adding some numbers to Troels' analysis...

The apparent depth is directly proportional to lateral displacement between the two views. This means that the apparent depth will be a product of the orbital radius, the orbital angular velocity, and an arbitrary constant that depends on the time separation. That third factor is responsible for flattening the perspective, but after that we can ignore it because it is the same for all elements of the image.

The surface of Jupiter has an equatorial radius of 71492 km (according to Wikipedia). With a rotational period of 9.925 hours, it has an angular velocity of 0.633 radians/hour. The product is a surface speed of 45259 km/hour.

For Ganymede, Wikipedia gives the orbital radius as 1070412 km, and orbital period as 7.1456 days/orbit. The angular velocity is 0.036638 radians/hour, for a speed of 39217 km/hour.

For Europa, Wikipedia gives orbital radius 671034 km and period 3.5512 days/orbit. The angular velocity is 0.073721 radians/hour, for a speed of 49469 km/hour.

In these images, all three objects are very close to being in a straight line with respect to us. So, their apparent depths with respect to the center of Jupiter will be in proportion to their lateral velocities: 45259 km/hour for the front surface of Jupiter, 39217 km/hour for Ganymede, and 49469 km/hour for Europa.

In the stereo pair, then, we should expect to see Europa as being a little closer than the front surface of Jupiter, by a ratio about 1:1.09, while Ganymede should appear a little behind the front surface of Jupiter, by a ratio about 1:0.87 . But Ganymede is seen against the edge of Jupiter, not its front, so we should expect to see Ganymede appear significantly in front of that edge, though slightly behind the front of the planet.

That is consistent with what I see and measure in the images, so at the moment I'm happy.

Yes, the relationship that we see in the stereo pair is very different from the physical relationship of the objects. But it's still a very cool effect!

Does anyone get a different result?

--Rik

Troels
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Re: Not really a macro

Post by Troels »

Rik,
I was sure you could do the precise calculations.
Forget my confusing attempts.
Troels Holm, biologist (retired), environmentalist, amateur photographer.
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rjlittlefield
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Re: Not really a macro

Post by rjlittlefield »

Troels wrote:
Tue Aug 31, 2021 10:43 am
I was sure you could do the precise calculations.
Hah! I did the calculations once, then I did them again and got the same answer, but things didn't look quite right, so I went over the whole process and discovered that I had screwed up and entered the wrong number in one place. Fixed that, went through the whole analysis again, got the same answer as after the fix, finally posted it. I'm very serious about that question, "Does anyone get a different result?" The chances are not nearly 100% that I have this right. :D #-o

--Rik

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Re: Not really a macro

Post by Cyclops »

Fantastic bringer of joy.
Canon 5D and 30D | Canon IXUS 265HS | Cosina 100mm f3.5 macro | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Slik 88 tripod | Apex Practicioner monocular microscope

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