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Offline JSS

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Re: How does FE explain star trails?
« Reply #40 on: January 29, 2021, 01:41:55 PM »
Quote
Prove it's not distorted.

Neither of us can prove anything with that photo because we don't know the details of the camera that took that photo

Actually, if there is a straight line reference in the photo, it will show whether the lens is producing distortion. Try again.

This is showing an incorrect understanding of how lenses work.

Here is a picture I just took with a fish eye lens, as you can see it too has a 'straight line reference' which is meaningless for proving other lines are not distorted, as they clearly are.

I'm sorry but random star trail pictures taken with unknown parameters you found on the internet are simply not proof that stars don't move in circles. If that is your only evidence, perhaps you should reconsider your conclusion.


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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #41 on: January 29, 2021, 07:11:08 PM »
The straight lines were not centered in the picture in the image of the farm provided. The lines on the elements of the farm were not centered. It appears that you are unable to adequately demonstrate your assertion.

Another rectilinear image. Lines are straight throughout the image:

https://fineartamerica.com/featured/mosquito-creek-star-trails-willard-sharp.html



Lines are straight:



Yet it is easy to see that the curves are not concentric circles:

Shift + Circle Tool in Paint.net:

« Last Edit: January 29, 2021, 08:20:16 PM by Tom Bishop »

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Offline stack

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Re: How does FE explain star trails?
« Reply #42 on: January 29, 2021, 07:59:11 PM »
Here's a neat one - Ultra wide-angle lens:



Timelapse of the shoot:



Polish photographer Bartosz Wojczyński pointed his camera straight at the north celestial pole and exposed his camera for a total of six hours...Wojczyński says he was photographing from the Teide Observatory on the Canary Islands, one of the world’s major observatories, from 8PM to 2AM...He captured 620 separate 35-second exposures using his Nikon D5100 and Samyang 10mm lens at ISO 1600 and f/4.8.
https://petapixel.com/2015/04/14/a-six-hour-long-exposure-of-the-celestial-north-pole/

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #43 on: January 29, 2021, 08:36:04 PM »
I don't see any evidence that that media wasn't edited for artistic reasons to get an ideal result. There aren't many straight line references at all.

Looks like an inability to find satisfactory evidence to me.

In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

http://bartoszwojczynski.com/picture-130704-startrails



The star trails in the image associated with that text certainly wouldn't be circular and concentric if the lens was highly warped like this (warped landmass, trees at odd angles on the sides of image) and there were circular concentric star trails in the sky:

« Last Edit: January 29, 2021, 09:20:27 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #44 on: January 29, 2021, 08:55:36 PM »
In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

That's color and contrast curves.  Geometric adjustments are called distortion correction.  You can't just do ctrl-f and look for a word without doing a little research to determine what it means in that context.

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Offline JSS

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Re: How does FE explain star trails?
« Reply #45 on: January 29, 2021, 09:05:44 PM »
The straight lines were not centered in the picture in the image of the farm provided. The lines on the elements of the farm were not centered. It appears that you are unable to adequately demonstrate your assertion.

How was I unable to demonstrate my assertion?

I showed you a picture that I just took showing straight lines and curved lines in the same image.  That proves my assertion that you can't just measure a straight line in one part of a picture and determine the rest is also straight.

You have not proven that your 'straight line measurements' work.  Show me a picture of a grid taken with that camera, with that lens, at the specific zoom as the star trails picture and show that there is no distortion.

You are also claiming photos that show non-circular images have no distortion, while claiming that images that show perfect circles are absolutely distorted. That's conformation bias.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #46 on: January 29, 2021, 09:07:54 PM »
In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

That's color and contrast curves.  Geometric adjustments are called distortion correction.  You can't just do ctrl-f and look for a word without doing a little research to determine what it means in that context.

Nope. "Curve" could mean any of several different things in Gimp, including the curves in the image.


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Offline stack

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Re: How does FE explain star trails?
« Reply #47 on: January 29, 2021, 09:10:23 PM »
I don't see any evidence that that media wasn't edited for artistic reasons to get an ideal result. There aren't many straight line references at all.

Looks like an inability to find satisfactory evidence to me.

In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

http://bartoszwojczynski.com/picture-130704-startrails



Ok, now I 100% know you're being wildly disingenuous and playing dumb regarding "curves" adjustments. You know exactly what "curves" does in GIMP, photoshop, and elsewhere. You've mentioned it before.

8.11. Curves
The Curves tool is the most sophisticated tool for changing the color, brightness, contrast or transparency of the active layer or a selection. While the Levels tool allows you to work on Shadows and Highlights, the Curves tool allows you to work on any tonal range. It works on RGB images.


So stop playing games like the, "Oh, lookee here, the photographer mentioned "curves" he must be making curves (circles) in post-production..." bullshit. My goodness, how low can you go? Just straight-up lying is a terrible look for you.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #48 on: January 29, 2021, 09:12:07 PM »
Wrong. The only person being disingenuous here is you. Modifying or adjusting curves could also refer with the curves in the image. - https://docs.gimp.org/2.10/en/plug-in-curve-bend.html

I also noticed that you blatantly ignored the other query. How did this warped picture from that author produce circular concentric star trails?

« Last Edit: January 29, 2021, 09:23:39 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #49 on: January 29, 2021, 09:23:22 PM »
In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

That's color and contrast curves.  Geometric adjustments are called distortion correction.  You can't just do ctrl-f and look for a word without doing a little research to determine what it means in that context.

Nope. "Curve" could mean any of several different things in Gimp, including the curves in the image.

So are you claiming that you know 100% that he is 'admitting' to adjusting the geometry of the picture in GIMP when he says 'curves adjustment'?  And not adjusting the color curves?

Even though distortion correction has a completely different name?  I doubt a professional photographer is going to mix up those terms.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #50 on: January 29, 2021, 09:27:56 PM »
In another star trail image that same artist, Bartosz Wojczyński, admits that he's making "curve adjustments" in GIMP:

That's color and contrast curves.  Geometric adjustments are called distortion correction.  You can't just do ctrl-f and look for a word without doing a little research to determine what it means in that context.

Nope. "Curve" could mean any of several different things in Gimp, including the curves in the image.

So are you claiming that you know 100% that he is 'admitting' to adjusting the geometry of the picture in GIMP when he says 'curves adjustment'?  And not adjusting the color curves?

Even though distortion correction has a completely different name?  I doubt a professional photographer is going to mix up those terms.

It could be either.

It literally says that you are modifying the curves in the tool.



Once again, how did this very warped picture from that author produce circular concentric star trails?

« Last Edit: January 29, 2021, 09:34:26 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #51 on: January 29, 2021, 09:37:54 PM »
It could be either.

It literally says that you are modifying the curves in the tool.



But once again, how did this warped picture from that author produce circular concentric star trails?



I'm not going to claim I know what you are thinking Tom, but 99% of anyone who knows how images are processed would understand him to be talking about color curves. If he was talking about lens distortion he would have said lens distortion.

As for how he got circular star trails on a warped picture, it is very simple to explain.

Lenses produce circular distortions and they are centered.

If he took a picture of concentric circles that were not centered, they would be distorted.

If he took pictures of concentric squares, they would be distorted.

If he took pictures of concentric triangles, they would be distorted.

See how the ground curves?  And the tree curves?  That's because those are not circles.

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Re: How does FE explain star trails?
« Reply #52 on: January 29, 2021, 09:52:35 PM »
Wrong. The only person being disingenuous here is you. Modifying or adjusting curves could also refer with the curves in the image. - https://docs.gimp.org/2.10/en/plug-in-curve-bend.html

I also noticed that you blatantly ignored the other query. How did this warped picture from that author produce circular concentric star trails?



You know you're being beyond disingenuous becasue I know you know what "curves" means in GIMP, photoshop, etc. As well, why didn't you post the technical specs for the photo I posted, which is right here:

Technical information
Location: Observatorio del Teide, Tenerife, Canary Islands
Date and time: 2015 March 14-15, 20:20 WET - 02:20 WET
Camera: Nikon D5100
Mount: Baader Astro & Nature tripod
Optics: Samyang AE 10 mm
Exposure: 620 x 34 sec., ISO 1600, f/4.8
Processing: Adobe Lightroom (NEF development); ProStack (stacking); Adobe Photoshop (curve adjustment)
http://bartoszwojczynski.com/picture-150315-startrails

See that in bold, Adobe Photoshop (curve adjustment). And I know you know what that refers to:


In short: You take specs from another photo and use it so it seems more ambiguous rather than using the specs from the actual photo where Photoshop "curve adjustment" means one thing only. And you know exactly what it means. Stop playing games.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #53 on: January 29, 2021, 10:09:57 PM »
I'm not going to claim I know what you are thinking Tom, but 99% of anyone who knows how images are processed would understand him to be talking about color curves. If he was talking about lens distortion he would have said lens distortion.

As for how he got circular star trails on a warped picture, it is very simple to explain.

Lenses produce circular distortions and they are centered.

If he took a picture of concentric circles that were not centered, they would be distorted.

If he took pictures of concentric squares, they would be distorted.

If he took pictures of concentric triangles, they would be distorted.

See how the ground curves?  And the tree curves?  That's because those are not circles.

So you believe it was taken with a fisheye lens and that he centered it dead on the center of rotation, as not to produce distortion. It's not centered, but lets pretend that it's a cropped photo and that it was centered.

This invalidates the claim of circular concentric star trails.

If you take a picture of an oval with a fisheye lens it becomes more circular.



Uploaded to the lunapic fisheye tool: https://www3.lunapic.com/editor/?action=fisheye

Now it's more circular:

« Last Edit: January 29, 2021, 10:19:18 PM by Tom Bishop »

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Re: How does FE explain star trails?
« Reply #54 on: January 29, 2021, 10:19:15 PM »
I'm not going to claim I know what you are thinking Tom, but 99% of anyone who knows how images are processed would understand him to be talking about color curves. If he was talking about lens distortion he would have said lens distortion.

As for how he got circular star trails on a warped picture, it is very simple to explain.

Lenses produce circular distortions and they are centered.

If he took a picture of concentric circles that were not centered, they would be distorted.

If he took pictures of concentric squares, they would be distorted.

If he took pictures of concentric triangles, they would be distorted.

See how the ground curves?  And the tree curves?  That's because those are not circles.

So you believe it was taken with a fisheye lens and that he centered it dead on the center of rotation, as not to produce distortion. It's not centered, but lets pretend that it's a cropped photo and that it was centered.

This invalidated the claim of observing circular concentric star trails.

If you take a picture of an oval with a fisheye lens it becomes more circular.

Tom. An oval is not a circle.

If you use a circular distortion on an oval it will distort, just like if you try it on a square.  A circular distortion on a circle will not distort the circle.

None of this even matters, because my picture proves you can't tell if an object is distorted or not by looking at lines elsewhere in the image. Every picture you use as proof that star trails are not circular is useless because you can't show what distortion may or may not be in the image as you didn't take the picture and don't know how it was done or what post processing was performed.

Star trails are circular, as all the calculations for predicting their location are circular and my telescope can find any star I want and they never show up somewhere else in the sky. Astronomers across the world would be having all kinds of trouble if the stars didn't behave the way math shows them to. And when I take pictures of star trails with lenses I know are free of distortion, and that I know are centered because I set it up, they also are circles.

You haven't shown any evidence to the contrary.  Unknown pictures you find on the internet are unreliable.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #55 on: January 29, 2021, 10:42:35 PM »
Tom. An oval is not a circle.

If you use a circular distortion on an oval it will distort, just like if you try it on a square.  A circular distortion on a circle will not distort the circle.

None of this even matters, because my picture proves you can't tell if an object is distorted or not by looking at lines elsewhere in the image. Every picture you use as proof that star trails are not circular is useless because you can't show what distortion may or may not be in the image as you didn't take the picture and don't know how it was done or what post processing was performed.

Star trails are circular, as all the calculations for predicting their location are circular and my telescope can find any star I want and they never show up somewhere else in the sky. Astronomers across the world would be having all kinds of trouble if the stars didn't behave the way math shows them to. And when I take pictures of star trails with lenses I know are free of distortion, and that I know are centered because I set it up, they also are circles.

You haven't shown any evidence to the contrary.  Unknown pictures you find on the internet are unreliable.

If you admit that a fisheye will make oval shapes more circular, and you think this guy is centering his warped lenses on the center of rotation, then it discredits the observation of circular star trails.

I don't see that there is anything further to discuss if you can't provide further corroborating information showing that the lens did not distort the star trails into circular shapes.

You know you're being beyond disingenuous becasue I know you know what "curves" means in GIMP, photoshop, etc. As well, why didn't you post the technical specs for the photo I posted, which is right here:

Technical information
Location: Observatorio del Teide, Tenerife, Canary Islands
Date and time: 2015 March 14-15, 20:20 WET - 02:20 WET
Camera: Nikon D5100
Mount: Baader Astro & Nature tripod
Optics: Samyang AE 10 mm
Exposure: 620 x 34 sec., ISO 1600, f/4.8
Processing: Adobe Lightroom (NEF development); ProStack (stacking); Adobe Photoshop (curve adjustment)
http://bartoszwojczynski.com/picture-150315-startrails

See that in bold, Adobe Photoshop (curve adjustment). And I know you know what that refers to:


In short: You take specs from another photo and use it so it seems more ambiguous rather than using the specs from the actual photo where Photoshop "curve adjustment" means one thing only. And you know exactly what it means. Stop playing games.

Pretty ambiguous. The same terminology of adjusting a curve can be used in Photoshop to mean geometric curves.

« Last Edit: January 29, 2021, 10:48:08 PM by Tom Bishop »

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Re: How does FE explain star trails?
« Reply #56 on: January 29, 2021, 10:57:49 PM »
Tom. An oval is not a circle.

If you use a circular distortion on an oval it will distort, just like if you try it on a square.  A circular distortion on a circle will not distort the circle.

None of this even matters, because my picture proves you can't tell if an object is distorted or not by looking at lines elsewhere in the image. Every picture you use as proof that star trails are not circular is useless because you can't show what distortion may or may not be in the image as you didn't take the picture and don't know how it was done or what post processing was performed.

Star trails are circular, as all the calculations for predicting their location are circular and my telescope can find any star I want and they never show up somewhere else in the sky. Astronomers across the world would be having all kinds of trouble if the stars didn't behave the way math shows them to. And when I take pictures of star trails with lenses I know are free of distortion, and that I know are centered because I set it up, they also are circles.

You haven't shown any evidence to the contrary.  Unknown pictures you find on the internet are unreliable.

If you admit that a fisheye will make oval shapes more circular, and you think this guy is centering his warped lenses on the center of rotation, then it discredits the observation of circular star trails.

I don't see that there is anything further to discuss if you can't provide further corroborating information showing that the lens did not distort the star trails into circular shapes.

You know you're being beyond disingenuous becasue I know you know what "curves" means in GIMP, photoshop, etc. As well, why didn't you post the technical specs for the photo I posted, which is right here:

Technical information
Location: Observatorio del Teide, Tenerife, Canary Islands
Date and time: 2015 March 14-15, 20:20 WET - 02:20 WET
Camera: Nikon D5100
Mount: Baader Astro & Nature tripod
Optics: Samyang AE 10 mm
Exposure: 620 x 34 sec., ISO 1600, f/4.8
Processing: Adobe Lightroom (NEF development); ProStack (stacking); Adobe Photoshop (curve adjustment)
http://bartoszwojczynski.com/picture-150315-startrails

See that in bold, Adobe Photoshop (curve adjustment). And I know you know what that refers to:


In short: You take specs from another photo and use it so it seems more ambiguous rather than using the specs from the actual photo where Photoshop "curve adjustment" means one thing only. And you know exactly what it means. Stop playing games.

Pretty ambiguous. The same terminology of adjusting a curve can be used in Photoshop to mean geometric curves.



Feel free to quadruple down. Everyone knows you know what "curve adjustment" in PS means. But for the record, even here, the same photographer uses "Adobe Photoshop (curve adjustment)" for this image:


Technical information
Location: Observatorio del Teide, Tenerife, Canary Islands
Date and time: 2015 March 15, 04:19 - 04:22 WET
Camera: Nikon D5300
Mount: Baader Astro & Nature tripod; Vixen Polarie
Optics: Samyang AE 85 mm
Exposure: 33 x 90 sec., ISO 1600, f/4.8
Processing: Adobe Lightroom (NEF development); DeepSkyStacker (alignment, stacking); Adobe Photoshop (curve adjustment)

http://bartoszwojczynski.com/picture-150315-centaurus-crux

Huh, curve adjustment where there are no circles to "curve"? Weird.

Stop playing games.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #57 on: January 29, 2021, 11:09:10 PM »
I don't see that you've proven anything about the true circular nature of the images. You've shown that he may be talking about one type of curve over another in a description.

I'm still waiting on the other query. If the photo was taken with a wide angle lens centered on the point of rotation, then it will turn oval shapes into more circular shapes, invalidating the premise.

I'm not going to claim I know what you are thinking Tom, but 99% of anyone who knows how images are processed would understand him to be talking about color curves. If he was talking about lens distortion he would have said lens distortion.

As for how he got circular star trails on a warped picture, it is very simple to explain.

Lenses produce circular distortions and they are centered.

If he took a picture of concentric circles that were not centered, they would be distorted.

If he took pictures of concentric squares, they would be distorted.

If he took pictures of concentric triangles, they would be distorted.

See how the ground curves?  And the tree curves?  That's because those are not circles.

So you believe it was taken with a fisheye lens and that he centered it dead on the center of rotation, as not to produce distortion. It's not centered, but lets pretend that it's a cropped photo and that it was centered.

This invalidates the claim of circular concentric star trails.

If you take a picture of an oval with a fisheye lens it becomes more circular.



Uploaded to the lunapic fisheye tool: https://www3.lunapic.com/editor/?action=fisheye

Now it's more circular:


« Last Edit: January 30, 2021, 04:14:03 PM by Tom Bishop »

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Re: How does FE explain star trails?
« Reply #58 on: January 29, 2021, 11:53:06 PM »
Tom. An oval is not a circle.

If you use a circular distortion on an oval it will distort, just like if you try it on a square.  A circular distortion on a circle will not distort the circle.

None of this even matters, because my picture proves you can't tell if an object is distorted or not by looking at lines elsewhere in the image. Every picture you use as proof that star trails are not circular is useless because you can't show what distortion may or may not be in the image as you didn't take the picture and don't know how it was done or what post processing was performed.

Star trails are circular, as all the calculations for predicting their location are circular and my telescope can find any star I want and they never show up somewhere else in the sky. Astronomers across the world would be having all kinds of trouble if the stars didn't behave the way math shows them to. And when I take pictures of star trails with lenses I know are free of distortion, and that I know are centered because I set it up, they also are circles.

You haven't shown any evidence to the contrary.  Unknown pictures you find on the internet are unreliable.

If you admit that a fisheye will make oval shapes more circular, and you think this guy is centering his warped lenses on the center of rotation, then it discredits the observation of circular star trails.

I don't see that there is anything further to discuss if you can't provide further corroborating information showing that the lens did not distort the star trails into circular shapes.

You have not understood my argument if you think I am saying that.  I am saying a circular distortion on a lens will not distort a circle.  You showed an oval which is not a circle, of course that will distort.

Why do I have to corroborate some random image on the internet I didn't even post?  I'm not trying to use random images to prove anything, I'm saying they are not useful.

I've said multiple times now you can't trust any random image on the internet to prove star trails are circular or oval.  Unless you take it yourself you can't know what was done to the picture either during or after it was taken.

You should find yourself a cheap star-finding telescope and try it out. You can see for yourself how it can find stars without trouble. If stars were moving in ovals instead of circles then it would be unable to find them. I've done this countless times and can assure you it works. Why would I lie about something anyone can verify for yourself? Thousands of people use these scopes every day. If that's too expensive, star finders on your cell phone are cheap, and free. Easy enough to verify that the stars are right where they should be. Moving in circles. Not ovals.


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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #59 on: January 30, 2021, 08:00:39 PM »
Quote
You have not understood my argument if you think I am saying that.  I am saying a circular distortion on a lens will not distort a circle.  You showed an oval which is not a circle, of course that will distort.

You're supposed to be arguing that the star trails are truly circular and not elliptical or oval. You claimed that the images showing non-circular star trails could have been affected by a warped lens. You guys then promoted the work of a photographer artist who you say is centering his warped lens on the center of rotation.

Yet, a wide angle lens will turn an oval shape into a more circular shape.

Oval:



Circle, showing that it is not a circle:



First image with the wide angle lens via Lunapic:

« Last Edit: January 30, 2021, 08:20:57 PM by Tom Bishop »