[Tom Bishop]

It goes both ways. If you are telling us that we can't trust random images because it's possible that they were modified then we can't trust random people who come to the forum who claim to have personal proof, because it is possible that it was modified.

In the first case you find it sufficient that you generally concede that you have no evidence that something was specifically modified, declaring it invalid because it is possible to be modified. In the second case you complain about evidence to see that something is modified, because it supports your belief to take that position. This sparks of hypocrisy.

No, two totally different scenarios. In the first, we just don't know if or how something was captured, modified, whathaveyou. In the second scenario it is explained if or how something was captured, modified, whathaveyou - You just don't believe the person.

Nope, they are not two radically different scenarios. In one scenerio you have no evidence that it was modified and declare that something is invalid based on zero evidence that something was modified. You are insisting that it is possible that it was modified, so it is invalid.

People have come here to lie before, asserting to be whistleblowers and spies and astronauts and everything of the sort, who have some sort of personal evidence that proves their point. Why should we not feel free to discard that evidence to be invalid due to circumstance, regardless of whether they show us a piece of paper which has the word NASA on it?

It is enough for you to disregard something because of a possibility, and it is hypocritical to claim that something can't be disregarded for another possibility.

[JSS]

It goes both ways. If you are telling us that we can't trust random images because it's possible that they were modified then we can't trust random people who come to the forum who claim to have personal proof, because it is possible that it was modified.

In the first case you find it sufficient that you generally concede that you have no evidence that something was specifically modified, declaring it invalid because it is possible to be modified. In the second case you complain about evidence to see that something is modified, because it supports your belief to take that position. This sparks of hypocrisy.

It's up to you if you want to disregard every bit of evidence that doesn't fit with your preconceived notions.

You are deliberately misconstruing the argument about random internet images. I never said you can't trust random people, I said if you don't know what lens a photo was taken with, what the settings were, what processing might have been done, then you can't use that photo as evidence that stars move in ovals.  It's not about trusting the image it's about the KNOWLEDGE and INFORMATION. You don't have either of those in this case.

Not because the photographer is a liar or dishonest, but because you do not have all the required information to determine if a curve is real or an artifact.  It's that simple.  You just don't know.

I trust my own photos because I took them, I know what lens I used, I know how I set it all up. There are no unknowns that could affect the outcome.

If you want to track down the photographers of all the pictures you used, ask them what lenses they used, what post processing they did, THEN you can use that image as evidence.

Otherwise you are just guessing and assuming, both which will lead you stray, as it has.

If you really want to know the truth about how stars move, read and try and understand my post on EQ mounts. That's solid proof right there, and you don't have to trust me at all. You can look it up yourself.

[stack]

It goes both ways. If you are telling us that we can't trust random images because it's possible that they were modified then we can't trust random people who come to the forum who claim to have personal proof, because it is possible that it was modified.

In the first case you find it sufficient that you generally concede that you have no evidence that something was specifically modified, declaring it invalid because it is possible to be modified. In the second case you complain about evidence to see that something is modified, because it supports your belief to take that position. This sparks of hypocrisy.

No, two totally different scenarios. In the first, we just don't know if or how something was captured, modified, whathaveyou. In the second scenario it is explained if or how something was captured, modified, whathaveyou - You just don't believe the person.

Nope, they are not two radically different scenarios. In one scenerio you have no evidence that it was modified and declare that something is invalid based on zero evidence that something was modified. You are insisting that it is possible that it was modified, so it is invalid.

People have come here to lie before, claiming to be whistleblowers and spies and astronauts and everything of the sort. Why should we not feel free to discard that evidence to be invalid, regardless of whether they show us a piece of paper which has the word NASA on it?

It is enough for you to disregard something because of a possibility, and it is hypocritical to claim that something can't be disregarded for another possibility.

I have no idea what you're talking about. I'm not "insisting" anything. All I said is that we don't know ANYTHING about an image that is randomly plucked from a google image search. It may be modified, it may not. Who knows unless you can dig up info from the shooter or elsewhere.

As for someone posting an image they took and describing what was done to it, gear used, etc., sure, take it at face value. And based upon that descriptive nature of the image or whatever and how it was assembled, at least you may have a shot to credit it or discredit it based upon the claimed details. The same applies to anything anyone posts/claims. At least you have some info to jump off from. In the first scenario, you have nothing.

[JSS]

The short version.

1. Do you have all the required information to make your determination?  In the case of a random internet image, no you do not.

2. If all the information is provided, do you trust the source?

Tom's images fall under category 1, mine under 2.

I can make sure 1 is covered when I post, but I can't do anything about 2.

[SteelyBob]

No. You are asking us to compare the two different orthogonal projections (A) and (B) in the above image from psu.edu, centered on Michigan and the Baltic countries, and see that they look different. This has no analogy to the question of whether a shape that the observer sees in the sky can be represented on a flat plane.

There is only one position we are comparing to the sky in the Stellarium projection of the sky, centered at a particular location. This is analogous to only comparing the shapes we see when looking down at a globe while we are hovered over the globe centered over Michigan and the orthogonal projection (A) when centered over Michigan.

Let's all remember - this is your analogy, and these are the two stellarium pictures you showed.

As can be clearly seen in the pictures, Polaris stays pegged in the same place, as we would expect, and everything else moves around it. And because everything has moved, they are no longer in the same place in the projection, which means the distance between them will change, even if their angular separation in the real sky remains the same. Just as the apparent width of the baltic states, or indeed any identifiable land mass, is different in those two globe projections, so it goes for the stars as well.

With every post, you go deeper into a hole of your own creation.

As an aside, I notice you've studiously avoided addressing JSS's point about the telescope mount, which is, frankly, one of the clearest and most obvious indications that stars move in circles. Aside from your own wiki post, of course...

[Tom Bishop]

Incorrect. Another false comparison. The location is the same, only the time is different.

The Orthogonal projection preserves shapes from a particular viewpoint. It doesn't matter if the scene is animated or not. The projection will be able to preserve the shapes seen by the observer.

[JSS]

Incorrect. Another false comparison. The location is the same, only the time is different.

The Orthogonal projection preserves shapes from a particular viewpoint. It doesn't matter if the scene is animated or not. The projection will be able to preserve the shapes seen by the observer.

What does it being animated or the time or location have anything to do with the problem that you can not measure distances on an orthogonal projection of a sphere as if it were a plane?

The issue at hand here is you are taking screenshots which are orthogonal projections of a sphere onto a plane, and trying to measure distances. This as you have seen does not work as the scale changes as you move away from the origin.  You can see the distortion in the trees and ground all curving inward.

Remember that the equation for orthogonal projection of a sphere uses transcendental functions, these are NOT linear, thus the result can't me measured as if they are.  This is this base mistake you are making.

All of which is still pointless to discuss since you have not addressed my EQ mount argument, which shows very simply that stars do move in circles, not ovals.

[Tom Bishop]

On telescope mounts, from an astronomy forum we read that a standard equatorial mount has limited use. Why should we believe your forum assertions over this person's?

https://www.cloudynights.com/topic/410655-equatorial-mount-for-beginner-and-other-advice/

Posted 13 March 2013 - 11:03 AM

"I'm a bit late to the thread, but my two cents on the 8SE: I'm relatively new to the hobby and the 8SE was my first purchase about a month ago. I think it's an amazing telescope for a newbie, but I quickly found myself wanting to photograph everything. The Alt/az mount it comes with can really only handle about 30-45 seconds of tracking an image to the point where stars aren't ovals. So getting those nice 300-600 second exposures I see some get here is not doable.

With that said, it's my first scope and I plan on enjoying this hobby for many more decades, so there will be time to get bigger and better. Going from just my two eyeballs to a nice 8" telescope is more than enough to keep me busy for good while.

Now I just need to find a good dark site to take it..."

Clearly an issue if some telescopes can handle 35 seconds and others 300 seconds.

[Tom Bishop]

You are misunderstanding what you read on that web page, perhaps you should look up more sources than a forum post from a new user who   

Once more, you are putting words into my mouth.  Where did I ever make claims about how useful or not basic entry level telescope mounts are?

The basic problem you seem to have here is you are confused about the limits of precision for cheap, hobby level equipment.

The other issue is you are confused over him saying 'oval stars' and you claim of 'oval star trails'.  This is due to the cheap mount not being stable and causing the telescope to not track accurately, causing teh stars to appear as a blur instead of sharp points.  A good setup will easily fix this problem, I can take 15-30 minute exposures with mine.

So in summary, you found someone complaining that their entry level telescope doesn't track as well as a professional scope.  This is both unsurprising, and has nothing to do with my argument, the quote does not conflict with anything I have said, once you look closer and understand it.

Did you really just Google 'oval' and 'EQ mount' and post the first quote you could find? 

Sorry, I don't see how your anonymous post is any more credible than another anonymous post.

[JSS]

On telescope mounts, from an astronomy forum we read that a standard equatorial mount has limited use. Why should we believe your forum assertions over this person's?

https://www.cloudynights.com/topic/410655-equatorial-mount-for-beginner-and-other-advice/

Posted 13 March 2013 - 11:03 AM

"I'm a bit late to the thread, but my two cents on the 8SE: I'm relatively new to the hobby and the 8SE was my first purchase about a month ago. I think it's an amazing telescope for a newbie, but I quickly found myself wanting to photograph everything. The Alt/az mount it comes with can really only handle about 30-45 seconds of tracking an image to the point where stars aren't ovals. So getting those nice 300-600 second exposures I see some get here is not doable.

With that said, it's my first scope and I plan on enjoying this hobby for many more decades, so there will be time to get bigger and better. Going from just my two eyeballs to a nice 8" telescope is more than enough to keep me busy for good while.

Now I just need to find a good dark site to take it..."

The EQ mounts clearly aren't all circular if some can handle 35 seconds and others 300 seconds.

Tom, look at the bold part of your quote.

He is talking about an Alt/az mount, not an equatorial mount.  They are completely different things.

It really looks like you just Googled 'oval' and 'eq mount' and copy-pasted the first quote you could find without reading or understanding it.

Besides, nothing in that quote contradicts anything I said.  Nobody has to choose to believe me over them because they are both true.

The other issue is you are confused over him saying 'oval stars' and your claim of 'oval star trails'.  He's talking about the stars being blurry shapes due to the lack of tracking precision.

[Tom Bishop]

He is talking about an Alt/az mount, not an equatorial mount.  They are completely different things.

I don't see the relevance. All components of a telescope need to be sufficient for star tracking. If some telescope users can only get 45 seconds and others 400 seconds, I don't see how it supports your case that we can just buy a telescope and track a star accurately all night long.

Please show direct third party evidence that the stars are trackable for long duration.

The other issue is you are confused over him saying 'oval stars' and your claim of 'oval star trails'.  He's talking about the stars being blurry shapes due to the lack of tracking precision.

No, lack of tracking precision wouldn't cause the telescope to become out of focus. It is clear what is being described there.

[JSS]

He is talking about an Alt/az mount, not an equatorial mount.  They are completely different things.

I don't see the relevance. All components of a telescope need to be sufficient for star tracking. If some telescope users can only get 45 seconds and others 400 seconds, I don't see how it supports your case that we can just buy a telescope and track a star accurately all night long.

Please show direct independent evidence that the stars are trackable for long duration.

Do you not understand the difference between an Alt/az mount and an equatorial mount?

The relevance should be blindingly obvious to anyone what does. The equatorial mount spins on it's axis in a circle to track the stars, the Alt/az mount does not.

You are confused that some users get better tracking with a telescope mount DESIGNED FOR BETTER TRACKING rather than a telescope designed to be cheap? Why is this a point of confusion for you?  If you want long term tracking, buy a mount designed for that.

Now you want to go down the rabbit hole of proving to you that telescopes can track stars for a 'long' duration.  Fine, but please specify what 'long' is so I don't waste my time, thanks.

[Tom Bishop]

You haven't provided any evidence that third parties are able to track stars all night long. You are only providing an interpretation of what you think is happening, and simply declaring what is possible. Some people are clearly having issues with their equipment, so your suggestion that we should buy random equipment and give it a try is invalid.

Show us the people who are not having issues, and have accurately tracked stars all  throughout the night.

[Kokorikos]

I think that we can all agree that the process that JSS followed to get his photos of the circular star trails is easily reproducible.

Why doesn't anyone else do the same to check the validity of his results?

[Tom Bishop]

Another reference, see bolded:

https://www.astropix.com/html/i_astrop/tracked/polar.html

"'Equatorial' telescope mountings have two axes, a polar axis and a declination axis, to help compensate for the Earth's rotation and aim at objects in different parts of the sky.

~

Use of a polar alignment scope built into the mount will help speed up alignment, but "drift" aligning will probably also be necessary for critical work.

A star that is monitored at high power (200x) in a guiding eyepiece with cross hairs most probably will not stay in one exact location in the field. There are several different reasons for this.

The star will usually seem to bump around a bit if the seeing is not that good. It can move all over the place on a very short time frame if the seeing is really bad.

Even if the seeing is excellent, the star will slowly drift from its original location. It can drift east - west due to inaccuracies in the right ascension gear and drive train that move the telescope to compensate for the Earth's rotation.

This is normally associated with periodic error, so called because the error in drift will coincide with the period of rotation of the worm gear. If a star is carefully monitored, the star will move one way for about 1/2 of the period of the worm, and then move back the other direction until it has returned to its starting position. This movement will usually be gentle and slow, but there can be quick jerks and movements from erratic error depending on the quality of the worm, gear, and components. For excellent mounts, this periodic error can be as little as a few arc seconds. For mediocre mounts, it can be as large as several minutes of arc.

For long-exposure deep-sky astrophotography, this periodic error must be guided out by either manually by the photographer with a high-power cross hair eyepiece or automatically with a CCD auto-guider such as the SBIG ST-4 or STV.

If the mount is not polar aligned to good accuracy, there will also be a slow north or south drift in declination.

Drift polar aligning is accomplished by monitoring the declination drift of a star at high power in the eyepiece and adjusting the polar axis of the mount based on the direction of drift.

Two corrections are necessary based on two observations: one of a star on the meridian for the azimuth of the polar axis of the mount, and one of a star near the eastern or western horizon for the elevation of the polar axis.

While monitoring the drift, any east - west movement is ignored or guided out by corrections in right ascension only. It is important that no corrections be made in any north - south declination drift because this drift will indicate which we have to move the mount to achieve more accurate polar alignment."

[JSS]

You haven't provided any evidence that third parties are able to track stars all night long. You are only providing an interpretation of what you think is happening, and simply declaring what is possible. Some people are clearly having issues with their equipment, so your suggestion that we should buy random equipment and give it a try is invalid.

Show us the people who are not having issues, and have accurately tracked stars all  throughout the night.

Tom, I said to use an equatorial mount, and you found someone having problems with an Alt/az mount.  Please learn the difference and why one tool is better than another for some purposes.

One of these mounts is designed for long term star tracking, the other is not. 

If I tell you to buy a screwdriver and you find people having trouble with hammers, how is that at all relevant?

You are clearly able to use Google, so I'm confused how you are unable to look up the ability of equatorial mount telescopes to track stars.

But if you would like me to do it for you I ask again, and please answer this time, what do you mean by proving they can track for a 'long' time?  And why do you need to track them all night?  An hour is plenty of time to get a good star trail picture.

[JSS]

Even if the seeing is excellent, the star will slowly drift from its original location. It can drift east - west due to inaccuracies in the right ascension gear and drive train that move the telescope to compensate for the Earth's rotation.

You got the right telescope mount this time at least.

But you still are confused about precision and physical limitations. The star drifts because of 'inaccuracies in the right ascension gear and drive train' not because the stars themselves are moving in ovals.

Your quote clearly indicates the errors are due to the limits of quality and tolerance in the equipment.

I'd also like to point out the other statement in your quote, 'to compensate for the Earth's rotation'. Your own source is also clearly indicating that the stars do rotate in circles, as they would on a rotating Earth.

[Tom Bishop]

The above quote was from an authoritative source astropix.com which says that even with excellent conditions there will still be drift with this sort of equipment.

None of this is compelling evidence that this equipment can accurately track a star all night long.

You have provided no legitimate evidence for this established nature of EQ mounts you were trying to pawn off.

You even resort to bolding "earth's rotation" as your center piece, because your level of evidence for this is weak.

[JSS]

The above quote was from an authoritative source astropix.com which says that even with excellent conditions there will still be drift with this sort of equipment.

None of this is compelling evidence that this equipment can accurately track a star all night long.

You have provided no legitimate evidence for this established nature of EQ mounts you are trying to pawn off.

You even resort to bolding "earth's rotation" as your center piece, because your level of evidence for this is weak.

I'm not trying to pawn off anything, millions of people use equatorial mount telescopes to track stars successfully.  Your only argument is you demand 100% accuracy?

You haven't explained why needing to track a star 'all night long' is required for you to believe a telescope can track stars?

Do you understand how precision works? No matter how precise you make a piece of physical equipment, there are always tolerances it will fail at.

No matter how much money you spend or how carefully building, anything physical will have physical errors and limitations.  Nothing in the world is 100% perfect.

You seem to be suggesting that if a telescope can 'only' track for 10 hours and not 10 hours and 1 second, then it can't track the stars at all?

You keep asking me to prove telescopes can track stars, but continue to refuse to narrow down your request so I can do so.

1. How many hours do you need for proof?

2. What amount of magnification?

My scope can certainly track stars all night long if I have a wide angle lens.  Less if I start to zoom in.

[Tom Bishop]

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.