[Tom Bishop]

A challenge to you, Tom. Based on the ruler which I assure you is straight in reality, tell me which way that cable is curved and by how much and how you have determined this.

No thanks. Not interested in engaging you any further. I have determined that you are most likely spamming this forum with whatever frivolous argument that you can make, and will justify that dogs are cats and up is down if you think it will help you. Kindly cease.

[stack]

I have no idea if the distortion in the image is in camera (lens) or was achieved in post, but there's definitely something going on. The bridge, though the i-beams are straight unto themselves, they sure slant in a very distorted way toward the left. See the red arrows as I would expect the beams to be:



Here's another one of the guy's photos - Same bridge. See what I mean:



All in all, they aren't really good examples because we don't know the lenses used and/or post-production effects employed. But there's definitely some distortion.

[Tom Bishop]

See the red arrows as I would expect the beams to be:

No. Vertical structures tilt if the camera is crooked and not parallel with the surface.

[Longtitube]

See the red arrows as I would expect the beams to be:

No. Vertical structures tilt if the camera is crooked and not parallel with the surface.

Whereas the star paths are unaffected? You see what you just said? Wow.

[JSS]

A challenge to you, Tom. Based on the ruler which I assure you is straight in reality, tell me which way that cable is curved and by how much and how you have determined this.

No thanks. Not interested in engaging you any further. I have determined that you are most likely spamming this forum with whatever frivolous argument that you can make, and will justify that dogs are cats and up is down if you think it will help you. Kindly cease.

My arguments are not frivolous nor spamming just because you say so. What exactly are you asking me to cease doing?

My argument is the same as always, you can't tell the distortion in one section of an image by measuring another if you don't know the exact properties of the lens and whatever post-processing may have been done.  This is very simple, and the picture is to provide an example.

You claim you can tell if stars are distorted or not because you measured something else in the image. If you can do that, why can't you do the same in my image? Refusing to even try simply shows you are unable to do so.

[Iceman]

Same bridge, same photographer, same stars. Circles added...to the circular paths...

[JSS]

Same bridge, same photographer, same stars. Circles added...to the circular paths...

Good find. I mentioned earlier in the thread that circular trails would not be distorted if centered in the lens. Nice to see an example from the same photographer of the same bridge.

It should be crystal clear now that the oval trails in his other images are indeed distorted by the lens, since the distortions only appear when the origin of the star trail circles is not centered in the frame.

[Tom Bishop]

The procedure described was to follow a long start trail rather than trying to wing it. However, these trails are a bit too short for that procedure anyway.

The circle overlaps trails in the image:

[JSS]

The procedure described was to follow a long start trail rather than trying to wing it. However, these trails are a bit too short for that procedure anyway.

What is the minimum length of a star trail to be valid for your procedure?  These trails seem to cover about 12 degrees.  How many degrees is needed?

[AATW]

I haven't really been following this tread tbh but is Tom arguing that star trails aren't circular? If so then I don't see how that really helps FE and on this Wiki page it says

The stars in the night sky trace almost perfect circles around the hub of the earth because by necessity the mechanics of a multiple system rely intimately on the movements and vectors of every member body. Circular movement is the most perfect, stable movement. If one celestial body is out of place or moves in a different fashion than the other bodies of the group the entire system becomes inherently imbalanced. Eddies, or stars that move out of tandem, will either leave the system entirely or are compelled by the stellar system to move back into its locked pace and apogee. This is why there are no elliptical orbits.

https://wiki.tfes.org/Star_Rotation

The bigger issue for FE is why the trails go in the opposite direction in the southern hemi-plane. This is to be expected on a sphere, you're "upside down" and thus going the other way around from your frame of reference. Not sure how that would work on a flat earth.

[SteelyBob]

I haven't really been following this tread tbh but is Tom arguing that star trails aren't circular? If so then I don't see how that really helps FE and on this Wiki page it says

The stars in the night sky trace almost perfect circles around the hub of the earth because by necessity the mechanics of a multiple system rely intimately on the movements and vectors of every member body. Circular movement is the most perfect, stable movement. If one celestial body is out of place or moves in a different fashion than the other bodies of the group the entire system becomes inherently imbalanced. Eddies, or stars that move out of tandem, will either leave the system entirely or are compelled by the stellar system to move back into its locked pace and apogee. This is why there are no elliptical orbits.

https://wiki.tfes.org/Star_Rotation

The bigger issue for FE is why the trails go in the opposite direction in the southern hemi-plane. This is to be expected on a sphere, you're "upside down" and thus going the other way around from your frame of reference. Not sure how that would work on a flat earth.

Great point!

I'm still waiting for Tom to explain my apparent misunderstanding of polar azimuthal projections and how, contrary to popular belief, you can make straight-line measurements on them and compare any two different parts of the projection without fear of distorted results.

[JSS]

I finally got a clear night and managed to capture some star trails.  I couldn't get to a really good location for a full sky view that wasn't blocked in some way, that will have to wait for spring.

I made sure that Polaris was centered in the frame so there would be no barrel distortion.

Tom never said how long the star trails need to be for his procedure, but hopefully these are long enough.

As you can see, these are circular.  They are not oval, they are not massively distorted, they do not look anything like the bridge pictures that were shown.

I made no distortion corrections to this image. It's not warped in any way. I did crop it and removed the horizon.

Overall I'm pretty happy with this, it shows what I wanted and is just in general, pretty to look at. I never took star trails perfectly centered before, I always tried to frame the picture to be interesting. So this was fun.

This experiment proves (if only to myself) that star trails are indeed circular. I know the camera, lens, setting and everything done to this image so there can be no doubt in my mind.  If anyone has questions, feel free to ask.

[AATW]

That is outstanding work. JSS.
I thought of something else this morning. If the stars are rotating above the plane of the flat earth and the rotation is about the centre of the disc then the only point at which they would trace circles in the sky is from the North Pole.
Anywhere else and you're "off centre" which would mean the circle they trace would be flattened from your point of view.
But that isn't what is observed, as you have shown,

[SteelyBob]

That is outstanding work. JSS.
I thought of something else this morning. If the stars are rotating above the plane of the flat earth and the rotation is about the centre of the disc then the only point at which they would trace circles in the sky is from the North Pole.
Anywhere else and you're "off centre" which would mean the circle they trace would be flattened from your point of view.
But that isn't what is observed, as you have shown,

Indeed - I keep making that point but it's usually ignored. If you go back to the FE modelling video that Tom posted earlier in this thread you'll see precisely that kind of elliptical shape in the star trails, which is kind of how we got onto this rather lengthy discussion around whether or not real star trails are circular.

There remains no credible FE explanation of how that circular rotation pattern is observed everywhere, with the centre point (ie the pole stars) of each changing elevation in response to moving observer latitude. And then of course it gets worse for FET when you throw in the southern celestial pole and the fact that it's always south regardless of where you view it from.

[JSS]

That is outstanding work. JSS.
I thought of something else this morning. If the stars are rotating above the plane of the flat earth and the rotation is about the centre of the disc then the only point at which they would trace circles in the sky is from the North Pole.
Anywhere else and you're "off centre" which would mean the circle they trace would be flattened from your point of view.
But that isn't what is observed, as you have shown,

Thanks!  That was hours and hours of work, although most of it was waiting.  I eventually got tired and had to go to bed. I've got some equipment on order to help with taking longer ones, now that I've gotten excited about doing it again. I do love this site for inspiring me. Wish the weather would cooperate though.

I am certainly not living at the north pole, far from it, so if the star paths were distorted away from it I would certainly see evidence of it here. 

In my opinion I think that photo is pretty definitive when it comes to answering the question here if stars go in circles or ellipses, unless someone can point out any major flaws in my technique. I think I covered everything though.

Back to the question at hand?  How does FE explain circular star trails?

[Longtitube]

I finally got a clear night and managed to capture some star trails.  I couldn't get to a really good location for a full sky view that wasn't blocked in some way, that will have to wait for spring.

I made sure that Polaris was centered in the frame so there would be no barrel distortion.

Tom never said how long the star trails need to be for his procedure, but hopefully these are long enough.

As you can see, these are circular.  They are not oval, they are not massively distorted, they do not look anything like the bridge pictures that were shown.

I made no distortion corrections to this image. It's not warped in any way. I did crop it and removed the horizon.

Overall I'm pretty happy with this, it shows what I wanted and is just in general, pretty to look at. I never took star trails perfectly centered before, I always tried to frame the picture to be interesting. So this was fun.

This experiment proves (if only to myself) that star trails are indeed circular. I know the camera, lens, setting and everything done to this image so there can be no doubt in my mind.  If anyone has questions, feel free to ask.

Yep, nice job.   I make the angle of rotation around 63 degrees, so using Bob Knodel's handy aide-memoire that makes an exposure of around 4 hrs 12 minutes?  That image would illustrate the wiki article quite nicely.

[JSS]

Yep, nice job.   I make the angle of rotation around 63 degrees, so using Bob Knodel's handy aide-memoire that makes an exposure of around 4 hrs 12 minutes?  That image would illustrate the wiki article quite nicely.

Nice job on the math.  I just checked the timestamps and you are dead on.  Exactly 4 hours 12 minutes between the first and last pictures used in this image.

I ended up giving up and going to bed eventually.  I'm too old to be able to go all night anymore.

I had to keep switching batteries every hour or so, which also ran the risk of bumping the camera. I've got a DC power supply on order for the next clear night which by my calculations will be in about 3 months. Sigh.

[Tom Bishop]

I finally got a clear night and managed to capture some star trails.

Your evidence isn't good around here. A moderator of this forum has branded you to be a compulsive liar, and you have blatantly lied in previous threads.

[SteelyBob]

I finally got a clear night and managed to capture some star trails.

Your evidence isn't good around here. A moderator of this forum has branded you to be a compulsive liar, and you have blatantly lied in previous threads.

I'm still waiting for Tom to explain my apparent misunderstanding of polar azimuthal projections and how, contrary to popular belief, you can make straight-line measurements on them and compare any two different parts of the projection without fear of distorted results.

[Tom Bishop]

I finally got a clear night and managed to capture some star trails.

Your evidence isn't good around here. A moderator of this forum has branded you to be a compulsive liar, and you have blatantly lied in previous threads.

I'm still waiting for Tom to explain my apparent misunderstanding of polar azimuthal projections and how, contrary to popular belief, you can make straight-line measurements on them and compare any two different parts of the projection without fear of distorted results.

This was addressed to you without answer:

Nope, I wasn't wrong at all. I looked as Stellarium and couldn't find circular star trails.

So you’re standing by taking linear measurements on a picture which has the normally flat line of the horizon wrapped around in a circle? You don’t see a problem with that exercise?

No. I just see a misunderstanding of the polar projection, and planispheres. If you were representing the 180 degree view of the sky on a piece of paper you would do so on a circle.

Indeed you might choose to do that. But if you were to attempt to use a ruler to try to infer the angle subtended at the eyes of an observer between any two points, then other than cases involving measurement from the centre of the azimuthal projection, you will get a wrong answer. As you have done in your example.

You don’t need to even understand azimuthal projections to grasp this - it’s pretty obvious if you think about it.

I would need to see more evidence that it is impossible to portray the shapes an observer sees when looking up at the domed concave celestial sky onto a flat circular plane.

Here is an inverse example with a RE globe. If you are looking down at a globe and saw the great lakes in the shape of a circle for argument's sake (drawn orange circle), why don't you think that this circular shape can be maintained in a projection?

https://gisgeography.com/azimuthal-projection-orthographic-stereographic-gnomonic/



It literally says that this projection simulates what the observer would see from that position over the globe.

If the observer is hovering over the globe (if it was a globe) and sees the shape of a circle in the United States (orange circle) from that position, why shouldn't it also be a circle in the associated flat projection described?