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Offline JSS

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Re: How does FE explain star trails?
« Reply #200 on: February 07, 2021, 06:52:24 PM »
It doesn't say anything about being accurate for ten hours. Find third party evidence which says that long-term tracking of the stars with an EQ mount is possible. You have provided nothing at all, except for your insistence that it is possible.

Tom, you demanding 100% accuracy is unreasonable.  I already explained that nothing physical at all is ever 100% accurate, nothing.

So why are you demanding equilateral mounts be absolutely perfect?  Can you at least acknowledge that you understand that nothing can be made perfectly accurate?  That's an important concept you need to understand first before we go further.

And why this ten hour magic number?  If I find a scope that can track for 9 hours you will reject it, but if I find one for 10 hours then you will accept it?  Why?  What's your method for determining that then hours is the required tracking time?  It seems like you just picked an arbitrarily high number.  Can you provide a reference, or show your math for why you picked ten hours?

You need to understand that at 10 hours, even the heating and cooling of the metal of the stand and the surface it rests on is going to make the tracking drift.  I don't think you fully comprehend the tolerances at play here.

You are demanding I prove something that is done by thousands of people around the world every single night.  If you want third party evidence, look it up.  If you still can't find it, I'll try and help.  But you need to be able to explain what you are looking for.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #201 on: February 07, 2021, 07:01:38 PM »
The page doesn't say anything about being accurate for 10 hours, or 9 hours either. You are the one who keeps trying to insist that it's accurate for long duration. You haven't shown that it's accurate for any length of time.

Where are the references and evidence showing that long duration tracking of a star with an EQ mount has occured?

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Offline JSS

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Re: How does FE explain star trails?
« Reply #202 on: February 07, 2021, 07:06:00 PM »
The page doesn't say anything about being accurate for 10 hours, or 9 hours either. You are the one who keeps trying to insist that it's accurate for long duration. You haven't shown that it's accurate for any length of time.

Where are the references and evidence showing that long duration tracking of a star with an EQ mount has occured?

So you will only accept the fact that equatorial mounts can track the stars if you can find third party evidence that it can track for 10 hours?  No less?

How much precision is required?  How much error due to mechanical tolerances will you accept?

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #203 on: February 07, 2021, 07:56:24 PM »
$700 Equatorial Mount - https://www.amazon.com/gp/product/B07NY44782/

https://www.amazon.com/gp/product/B07NY44782/ref=ask_ql_qh_dp_hza

"Question: When polar aligned north, can you use a ball head mount to rotate your camera 180* to capture the southern sky without trailing?

Answer: Hi Doyle, YES! Once the head is aligned, move your camera wherever and it will track the object for up to 5 minutes when using a wide-angle the lens. A telephoto (200mm) can only go about 2 minutes."

Seems to suggest that this $700 EQ mount can only track stars for up to 5 minutes.
« Last Edit: February 07, 2021, 08:10:01 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #204 on: February 07, 2021, 08:05:12 PM »
$700 Equatorial Mount - https://www.amazon.com/gp/product/B07NY44782/

From the Q&A:

https://www.amazon.com/gp/product/B07NY44782/ref=ask_ql_qh_dp_hza

"Question: When polar aligned north, can you use a ball head mount to rotate your camera 180* to capture the southern sky without trailing?

Answer: Hi Doyle, YES! Once the head is aligned, move your camera wherever and it will track the object for up to 5 minutes when using a wide-angle the lens. A telephoto (200mm) can only go about 2 minutes."

Seems to suggest that this $700 EQ mount can only track stars for up to 5 minutes.

What exactly is the point you are trying to make here? A mid-level telescope without a solid stand is going to give you 2-5 minutes of tracking which is quite good for near entry level equipment.  If you think $700 is expensive, you have not seriously shopped for astronomy equipment.  If you think 'on;y' 5 minutes is terrible, it means you don't understand the precision required for more.

You seem to be thinking that after 5 minutes the stars will go veering widely out of the view frame, this is wrong.  I'm not sure what you imagine is going on here, but you are not understanding what they mean when they say it can only track for 5 minutes.

What happens is after 5 minutes the inaccuracies are enough to make the stars blurry, which ruins the image.  Usually the errors are cyclical, which results in fuzzy stars, but the stars do not go careening wildly all over the image frame.  At the end of even several hours, the stars will still be quite well aligned in the viewfinder/camera.

You bolded 'move your camera wherever' which seems you indicate you don't understand this either.

Your own source here states quite clearly the mount DOES track the stars, it just has limits for how steady it is and that the jitter will start to blue stars after a few minutes.  This in no way means it can't track the stars, nor does it means stars travel in ellipses.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #205 on: February 07, 2021, 08:23:01 PM »
Quote
What happens is after 5 minutes the inaccuracies are enough to make the stars blurry, which ruins the image.  Usually the errors are cyclical, which results in fuzzy stars, but the stars do not go careening wildly all over the image frame.  At the end of even several hours, the stars will still be quite well aligned in the viewfinder/camera.

It doesn't say that in the link.

Once more, you continue to provide zero sources on this assertion that these mounts have accurately followed stars over long duration.

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Offline JSS

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Re: How does FE explain star trails?
« Reply #206 on: February 07, 2021, 08:23:40 PM »
Quote
What happens is after 5 minutes the inaccuracies are enough to make the stars blurry, which ruins the image.  Usually the errors are cyclical, which results in fuzzy stars, but the stars do not go careening wildly all over the image frame.  At the end of even several hours, the stars will still be quite well aligned in the viewfinder/camera.

It doesn't say that in the link.

Once more, you continue to provide zero sources on this assertion that these mounts can accurately follow stars over long duration.

Yes it does say that, you just don't understand enough to understand the context. You are looking at these pages and discussions made by people who actually use this equipment and are making a lot of assumptions based on ignorance of the subject.

Your insistence on a 'long duration' doesn't prove they don't track stars, it just means you don't understand the precision alignment required to track stars with extreme precision without any drift that can be seen by today's high resolution sensors.  You really should look at the numbers on just HOW accurate these devices are.  Saying you 'only' get 5 minutes before the stars start to blue shows you don't really understand this.

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #207 on: February 07, 2021, 08:58:17 PM »
Yes it does say that

Quote it then. You are merely coming up with "explanations" which are stated nowhere in the text.

Once again, you continue to provide zero evidence from third party sources that stars have been tracked for long duration.

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Offline JSS

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Re: How does FE explain star trails?
« Reply #208 on: February 07, 2021, 09:22:06 PM »
Yes it does say that

Quote it then. You are merely coming up with "explanations" which are stated nowhere in the text.

Once again, you continue to provide zero evidence from third party sources that stars have been tracked for long duration.

He said you can track stars for between 2-5 minutes.  This means it takes 2 to 5 minutes to drift enough to be noticeable on a high resolution camera. It does NOT mean the stars just veer into massive oval shapes or go wandering all over.  Your source backs me up that equatorial mounts do indeed track stars, and go in circles.

You are the one making unreasonable and vague demands that they track them for '10 hours' without giving any other specifics like error allowed and what kind of drift you find acceptable.

Let me try and explain so you can understand what's going on and why you are wrong here.

When you align an equatorial mount telescope you have to align the main axis perfectly with the rotation of the earth/sky.  Just aiming it at the pole star isn't good enough as the pole star is close, but not exactly in the center.  You can see this in the image I posted.

Note that this is NOT aiming the telescope!  This is lining up the actual motor and shaft of the mount, a much harder process to eyeball.

Once you think you have your mount leveled and aimed correctly, you attach your camera/telescope to it and take a long exposure. It's going to have drift because you didn't get it perfectly aligned, so you adjust it and try again. This process can take up to an hour depending on hos precise you want.

How precise is it?  Lets take that 2 minute exposure of the $700 telescope you googled.  Using an APS-C format DSLR and a 200mm lens as described, each pixel of the sensor covered 0.0008 degrees of the sky.  So that means in 2 minutes, that mount needs to rotate with THAT degree of accuracy.

So when they say they can 'only' get 2 minutes of shutter time, they mean it can keep it's alignment to within 1/10,000th of a degree over 2 minutes.  That is VERY good for $700 without a heavy duty tripod.

And you want ten hours!  That's just nuts.

Do you see why this is a unreasonable demand of yours?  You don't understand what you're even asking for.

And let me remind you that there are multiple sources of error from the various worm and normal gears. Some of that error is cyclic, other is linear. Every mount and motor will be different, different camera and telescope weights and how they are distributed will alter this error and how it is perceived.

If you take the worst case and all the error ends up pushing it off in the same direction, after ten hours that mount will only be off by less than 1/2 a degree. 

This is for a 'cheap' $700 scope sold without a heavy duty tripod.  More money gets you even higher precision. 

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #209 on: February 07, 2021, 09:35:30 PM »
No, I don't want rambling explanations from a random person on the internet, which is not stated in the text, and is of questionable veracity.

I want citations from authoritative sources that the EQ mount has tracked stars over long duration.

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Offline stack

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Re: How does FE explain star trails?
« Reply #210 on: February 07, 2021, 09:36:37 PM »
Yes it does say that

Quote it then. You are merely coming up with "explanations" which are stated nowhere in the text.

Once again, you continue to provide zero evidence from third party sources that stars have been tracked for long duration.

Here's a neat one:

Earth's Rotation Visualized in a Timelapse of the Milky Way Galaxy - 4K


A timelapse of the Milky Way that was recorded using an equatorial tracking mount over a period of around 3 hours to show Earth's rotation relative to the Milky Way.
Gear Used:
Camera https://amzn.to/33aQRe6
Lens https://amzn.to/39MCZt3
Lens Adapter https://amzn.to/2wNi4Yi
Tripod https://amzn.to/2vjN8i4
Tracking Mount https://amzn.to/39GOQc6
Intervalometer https://amzn.to/3aKRBJB
External Battery https://amzn.to/39UPkM5

EXIF: 24mm, 10", F/2.8, 16000iso.

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Offline JSS

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Re: How does FE explain star trails?
« Reply #211 on: February 07, 2021, 09:46:09 PM »
No, I don't want rambling explanations from a random person on the internet, which is not stated in the text, and is of questionable veracity.

I want citations from authoritative sources that the EQ mount has tracked stars over long duration.
I'm trying to explain how these work, I'm trying to teach you something but I can only provide the information, I can't make you understand it.  That's up to you.

If posting Wiki links is the only valid method of debate acceptable to you, then here you go.  Do your own research. https://en.wikipedia.org/wiki/Equatorial_mount

Stack posted a video, long-term tracking on an equatorial mount.  Is that good enough?


Offline SteelyBob

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Re: How does FE explain star trails?
« Reply #212 on: February 07, 2021, 10:04:09 PM »
No, I don't want rambling explanations from a random person on the internet, which is not stated in the text, and is of questionable veracity.

I want citations from authoritative sources that the EQ mount has tracked stars over long duration.

The internet is littered with excellent explanations of EQ mount errors. They explain very clearly what JSS is saying - you can't infer long-term error from the exposure lengths being discussed for several reasons. As JSS says, for a start the errors involved are tiny. Moreover, a big chunk of the error is periodic, meaning it might trash a long-isn exposure of a few minutes, but it will be no worse over 2 hours than 2 minutes.

Here's an interesting one I found very quickly by searching for 'EQ mount errors'.

http://www.pk3.org/Astro/index.htm?astrophoto_mount_errors.htm

The authors measures tracking error on their rig and breaks out the linear error from the periodic. The linear error looks to be around 150 arc seconds over 20 minutes, which is therefore 4500 arc seconds over 10 hours, or 1.25 degrees. That's pretty respectable, given that typical visible constellations are several degrees across - Orion is roughly 10 x 20 degrees - and way, way less than we would expect if the stars were moving in some kind of ellipse.

If the stars were moving elliptically, I'm pretty sure one of the millions of people who look at the stars for fun, or for a living, would have made a name for themselves inventing an elliptical tracking mount. But they haven't, have they?

I'd also point to the many 'go to' mounts you can buy, which use the same logic, based on the earth's rotation and the observer's location, to quickly move the scope to points of interest in their database.


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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #213 on: February 07, 2021, 10:30:41 PM »
The mount in that video is an advanced tracking mount like described would be necessary on the astropix.com site. It isn't merely a motor that goes in a circle. It can be connected to computers, uses cameras for tracking, and has add-ons that track and guide.

https://www.altairastro.com/ioptron-skyguider-pro-camera-mount-full-package-2227-p.asp

"For more advanced users who want extra-long exposures and or have longer focal length lenses, the built-in autoguiding port allows even more accurate tracking with an external guide camera such as the popular Altair GPCAM2 Mono."

There is another device in that package that has a camera as well: https://optcorp.com/products/ioptron-ipolar-skyguider-pro?rfsn=3263575.8c059d&utm_source=refersion&utm_medium=affiliate&utm_campaign=3263575.8c059d

The author linked to an amazon page which says "full package" in the title, which is now dead. These things usually have different package options listed, which can be selected from.

I see nothing really to indicate that the author selected any particular degraded set-up for this device and used a degraded mode which supports your circular motor idea.

Usually if you're going to buy an advanced package like this, you want to use its full features.

Also, the stars aren't even in the same position on the screen throughout the video.
« Last Edit: February 07, 2021, 10:35:56 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #214 on: February 07, 2021, 10:49:12 PM »
The mount in that video is an advanced tracking mount like described would be necessary on the astropix.com site. It isn't merely a motor that goes in a circle. It can be connected to computers, uses cameras for tracking, and has add-ons that track and guide.

https://www.altairastro.com/ioptron-skyguider-pro-camera-mount-full-package-2227-p.asp

"For more advanced users who want extra-long exposures and or have longer focal length lenses, the built-in autoguiding port allows even more accurate tracking with an external guide camera such as the popular Altair GPCAM2 Mono."

There is another device in that package that has a camera as well: https://optcorp.com/products/ioptron-ipolar-skyguider-pro?rfsn=3263575.8c059d&utm_source=refersion&utm_medium=affiliate&utm_campaign=3263575.8c059d

The author linked to an amazon page which says "full package" in the title, which is now dead. These things usually have different package options listed, which can be selected from.

I see nothing really to indicate that the author selected any particular degraded set-up for this device and used a degraded mode which supports your circular motor idea.

Usually if you're going to buy an advanced package like this, you want to use its full features.

Also, the stars aren't even in the same position on the screen throughout the video.

You said...

"I see nothing really to indicate that the author selected any particular degraded set-up"

then...

"the stars aren't even in the same position on the screen throughout the video"

I would suggest that if the stars are visibly shifting through the video, that is actually "something to really indicate" he didn't use the full star-tracking capabilities.  Otherwise there would be no shifting at all.

Tom, you have provided no compelling evidence that these mounts do not work exactly as advertised.  You keep demanding proof, but provide none in return, and have ignored everything I've tried to teach you on the subject.

You could spend $50 on a super cheap equatorial tracking mount and run your own experiments.  Or visit the local astronomy club, I've suggested this before.  You can see these things with your own eyes if you don't trust anyone on the internet.

I do recall this site encourages people to understand and familiarize themselves with the wiki pages of subjects they wish to discuss in detail.

Re: How does FE explain star trails?
« Reply #215 on: February 08, 2021, 09:19:11 AM »
It doesn't say anything about being accurate for ten hours. Find authoritative third party evidence which says that long-term tracking of the stars with an EQ mount has occured. You have provided nothing at all, except for your insistence that it is possible.
Why are you continuing to argue that the stars don't go in circles when your Wiki, which you wrote, says they do?
Do you just argue with anything anyone says for the sake of it whether it agrees with arguments you've previously made or not? ???

Just Googling things and bolding the parts which you think backs up your view - even if other non-bolded parts completely contradict it - is not an honest way of arguing. And the fact that the initial article you found wasn't even talking about the right kind of mount shows you're not arguing in good faith.

Are you arguing just for the sake of it or do you think the notion that the stars don't move in circles (again, your Wiki says they do) in some ways helps FE? How does it?

Your continued inability to address other issues like the angular size and magnitude of stars being constant despite them being in your model at significantly different distances throughout the night sky is telling.
"On a very clear and chilly day it is possible to see Lighthouse Beach from Lovers Point and vice versa...Upon looking into the telescope I can see children running in and out of the water, splashing and playing. I can see people sun bathing at the shore
- An excerpt from the account of the Bishop Experiment. My emphasis

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Offline Tom Bishop

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Re: How does FE explain star trails?
« Reply #216 on: February 10, 2021, 08:41:53 PM »
Quote from: JSS
I would suggest that if the stars are visibly shifting through the video, that is actually "something to really indicate" he didn't use the full star-tracking capabilities.  Otherwise there would be no shifting at all.

No, a delay or misfunction could be appropriated to many causes. This suggestion is bunk. If the device can optically track the stars, then we have to assume that it's optically tracking the stars.

Quote from: JSS
Tom, you have provided no compelling evidence that these mounts do not work exactly as advertised.

They are not advertised to track the stars for a long period of time. The EQ mount I posted advertised "up to 5 minutes".

Quote
Why are you continuing to argue that the stars don't go in circles when your Wiki, which you wrote, says they do?

Actually, it doesn't talk about that subject and makes no statements on the POV of the observer.

Quote
Your continued inability to address other issues like the angular size and magnitude of stars being constant despite them being in your model at significantly different distances throughout the night sky is telling.

It's pretty telling that you are unaware that the size of the stars are illusions in RE, and do not follow the angular size with distance rule of perspective - https://wiki.tfes.org/Star_Size_Illusion
« Last Edit: February 10, 2021, 08:47:43 PM by Tom Bishop »

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Offline JSS

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Re: How does FE explain star trails?
« Reply #217 on: February 10, 2021, 09:48:16 PM »
Quote from: JSS
I would suggest that if the stars are visibly shifting through the video, that is actually "something to really indicate" he didn't use the full star-tracking capabilities.  Otherwise there would be no shifting at all.

No, a delay or misfunction could be appropriated to many causes. This suggestion is bunk. If the device can optically track the stars, then we have to assume that it's optically tracking the stars.

Your suggestion is bunk, you are now claiming that if a device CAN perform a function it MUST perform the function... even if the video clearly shows it is not. The optical tracker can be turned off or even removed, this is a fact.

That is very bad logic.

Quote from: JSS
Tom, you have provided no compelling evidence that these mounts do not work exactly as advertised.

They are not advertised to track the stars for a long period of time. The EQ mount I posted advertised "up to 5 minutes".

Here you are making up an unreasonable demand, that an EQ mount must be able to track stars with 100% perfect accuracy for 10 hours, then saying because they can't meet this made-up demand of yours, that they can't track stars at all.

This is another case of very bad logic.

You have made up your own definition of 'long time' that is based on your ignorance of what the astrophotography community's standards agree on. Five minutes on a 200mm telephoto IS a long time.

EQ mounts can track stars all night, they just drift due to mechanical errors.  I have tried to explain the precision required but you seem to have not read it and just called it 'rambling'.  GO back and read my post again, it explains the difficulties of aligning something perfectly with the axis of the earth to match it's rotation to the point a sub-micron pixel stays stable.  I'm sorry you don't seem to understand precision and the limits of physical systems.

Googling random message boards and copy-pasting bits of conversation that you do not have the context to understand is not a good argument.

Offline SteelyBob

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Re: How does FE explain star trails?
« Reply #218 on: February 10, 2021, 10:32:41 PM »
Quote from: JSS
I would suggest that if the stars are visibly shifting through the video, that is actually "something to really indicate" he didn't use the full star-tracking capabilities.  Otherwise there would be no shifting at all.

No, a delay or misfunction could be appropriated to many causes. This suggestion is bunk. If the device can optically track the stars, then we have to assume that it's optically tracking the stars.

Quote from: JSS
Tom, you have provided no compelling evidence that these mounts do not work exactly as advertised.

They are not advertised to track the stars for a long period of time. The EQ mount I posted advertised "up to 5 minutes".

Quote
Why are you continuing to argue that the stars don't go in circles when your Wiki, which you wrote, says they do?

Actually, it doesn't talk about that subject and makes no statements on the POV of the observer.

Quote
Your continued inability to address other issues like the angular size and magnitude of stars being constant despite them being in your model at significantly different distances throughout the night sky is telling.

It's pretty telling that you are unaware that the size of the stars are illusions in RE, and do not follow the angular size with distance rule of perspective - https://wiki.tfes.org/Star_Size_Illusion

I note you're completely ignoring my post above where I showed a projected 10-hour tracking error of just over 1 degree for a decent EQ mount.

You seem to have completely failed to grasp the distinction between taking a good photo of a star (hence 5 minutes and other low numbers) and tracking a star adequately enough to be able to find it - the two things are very different. Likewise, the concept of periodic and cumulative errors is also passing right over you.

If the stars were moving in the kind of ellipses that your youtube fantasists were illustrating in their video, then we would be seeing way, way bigger errors than the numbers shown in those graphs. The fact that we don't is telling.

As for accusing that other video of employing star tracking - that's just laughably ridiculous, and completely missing the point. The thing to take away from that video is that the entire celestial picture is moving as one undistorted body - there's no visible change at all in the relationship between the stars. It's so far away from what your modelling videos it's ridiculous. And you can observe that yourself on any clear night.

To be honest, I'm just trying to work out if you actually, genuinely don't understand this, or if you're just engaged in some kind of wind-up. Either way...odd.

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Offline JSS

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Re: How does FE explain star trails?
« Reply #219 on: February 10, 2021, 11:43:22 PM »
As for accusing that other video of employing star tracking - that's just laughably ridiculous, and completely missing the point. The thing to take away from that video is that the entire celestial picture is moving as one undistorted body - there's no visible change at all in the relationship between the stars. It's so far away from what your modelling videos it's ridiculous. And you can observe that yourself on any clear night.

I'm going to have to make a video like this once I get some good weather and can sit outside for several hours.  You're right, it's a perfect example of how the stars move completely together, no ovals possible since the stars are motionless and rotating all at once.