Magnification clarity needed

[Stub Mandrel]

2 hours ago, Stu said:

My understanding is that the scope magnifies the angle subtended by the object by the specified amount eg something which is 0.1 degrees across will appear to be 2.5 degrees across if magnified by 25. To me that's making it 25 times larger!

in the old days they used the specify the magnification as 25 diameters which is not the same as 25 'areas'.

It think most people would say a lawn 25 meters by 25 metres was 625 times as big as a 1 x1 lawn.

Here's an example - 2 x magnification makes the square twice as high, but also twice as wide so it's four times as big.

Think about it - look at the moon using 25x and you see a lot more than 25 times as much detail.

(All the more reason to use binoviewers, at 25x they make planets look 15,625 times bigger )

[Stu]

19 minutes ago, Charic said:

You can't see much detail on the Planets  or anything else in Space because their just too far away, your eyes are not big enough to gather enough light to make out any fine detail, except the Moon maybe? 

What you need are bigger eyes, so in comes the telescope. The telescope is great for capturing light, and to be honest, the bigger or more  aperture it has, the more light it can gather, no matter what type of telescope?

This gathered light creates a real image, which is directed/ focused  to a place  known as the focal point, in my case, somewhere in the focus tube assembly?

Now by using an eyepiece, it allows me to see this image in some detail with my own eyes. Now I don't expect Jupiter to look 200x bigger than I can see with the naked eye ( I wish )  but by dividing my telescopes focal length by the focal length of the eyepiece in use, it  tells me that I am using/needing 200x magnification to see the tiny image, presented to my eye,  that,  which was formed at the focal point,  if  I chose to use  a 6mm eyepiece on  this occasion.

By changing the focal lengths of my eyepieces, I will apply magnifications greater or lesser than the 6mm in use.

There are limits too! Too much magnification just spreads out the image making it appear blurry, washed out, too little,  and not enough detail?

As much as I would like to see Jupiter 200x bigger than its physical size in the night sky, what  I am experiencing is a variation of  magnifications from about 375x down to  37x power/mag depending on my target subject and how much field of view I require. I just use the eyepiece on the night that offers the best detailed view visually, rather than working the maths, that can come later.

HTH.

I seem to be missing something here.

When I use 200 times magnification, my understanding is exactly that, I see the object at 200 times the size I see it with the naked eye. Is that not the case?

Jupiter is tiny, and you cannot even see the Gallilean moons or percieve it as a disk with the naked eye, yet with x200 I see it as a disk, with the moons separated by most of the fov with fine detail in the disk? Seems like a reasonable perception of x200 to me.

[Charic]

Stu............dont think your missing anything. 

I see magnification as the power required  to see the tiny focal  image, as a simple way of explaining how magnification works in a scope. I have always complained to my self how small Jupiter appears in my scope, and only a larger scope ( so I believe ) can improve the image scale to something more desireable for my needs, but bigger scopes also have their faults? seems I'm stuck with my f/6 for a while longer.

 

[Stu]

2 minutes ago, Charic said:

Stu............dont think your missing anything. 

I see magnification as the power required  to see the tiny focal  image, as a simple way of explaining how magnification works in a scope. I have always complained to my self how small Jupiter appears in my scope, and only a larger scope ( so I believe ) can improve the image scale to something more desireable for my needs, but bigger scopes also have their faults? seems I'm stuck with my f/6 for a while longer.

 

But...and I'm sorry to labour the point..... are we agreed that if I am using x200, then I am seeing an image which is 200 times bigger than with the naked eye? My belief is that yes, you are.

[Moonshane]

If something is 200x bigger then the area will naturally be more than 200x as you are working at dimensions squared but the diameter is of course 200x bigger in a circle and the side length 200x more in a square so in any normal sense it is 200x bigger than with naked eye. You would generally say a 6'  man is twice the size of a 3' child but if you work out the area in a photo this would be different again.  I have never heard anyone refer to the man as being four times the surface area of the boy.

[LukeSkywatcher]

1 hour ago, Moonshane said:

 

Has to be the best Fr. Ted ever.

[Charic]

1 hour ago, Stu said:

But...and I'm sorry to labour the point..... are we agreed that if I am using x200, then I am seeing an image which is 200 times bigger than with the naked eye? My belief is that yes, you are.

.....no worries. and i`m not sure?

The image produced by the telescope itself is real-time, real scale, 1-1.  By using x200 you are  magnifying a tiny image by a factor dictated by the sum of the telescope fo / fe  = x mag to achieve the detail you perceive with your eyes from that real image, and from this  I believe you/we  are looking at the focal image at 200x its original size, but in comparison to the image scale alone, using the naked eye , I don't think ( if we pick on Jupiter)  its actually looks 200x bigger ?

There are several  videos on the tube regarding linear and angular magnifications that try to help make things a little easier to understand, for a physicist ? I hope to learn a little more on the subject, as nothing is so simple in this hobby.

 

[Stub Mandrel]

1 hour ago, Moonshane said:

If something is 200x bigger then the area will naturally be more than 200x as you are working at dimensions squared but the diameter is of course 200x bigger in a circle and the side length 200x more in a square so in any normal sense it is 200x bigger than with naked eye. You would generally say a 6'  man is twice the size of a 3' child but if you work out the area in a photo this would be different again.  I have never heard anyone refer to the man as being four times the surface area of the boy.

I have a labrador that weighs 30 kilos and a cat that weighs about 3 kilos. The dog is about twice as long as the cat.

Sticking to planets, two (feeble) photos of Jupiter, the diameter difference is exactly 25 times, the area difference is 625 times. I think the one on the left looks more than 25 times bigger and has vastly more than 25 times as much detail.

[Ricochet]

2 hours ago, Stu said:

But...and I'm sorry to labour the point..... are we agreed that if I am using x200, then I am seeing an image which is 200 times bigger than with the naked eye? My belief is that yes, you are.

Yes. If you look at the moon with the naked eye it has an angular diameter of 0.5 degrees. If you then use a Plossl or any other 50 degree eyepiece that gives 100x magnification with your telescope you will find that it fills the entire view.

[cloudsweeper]

Say mag is x100.  That's like the same sized object at one-hundredth the distance OR a hundred times the object size at the same distance away.  

These are equivalent ways of seeing the matter.

But where IS the image?  According to the physics, it's a virtual one, at infinity, so it's difficult to think in terms of sizes and distances, and probably easier just to think in terms of angles subtended.  The familiar ratio of focal lengths formula for magnification does in fact give the angle subtended at the eye by the final image divided by the angle subtended at the naked eye by the object.

Doug.

 

 

[Moonshane]

9 hours ago, Stub Mandrel said:

I have a labrador that weighs 30 kilos and a cat that weighs about 3 kilos. The dog is about twice as long as the cat.

Sticking to planets, two (feeble) photos of Jupiter, the diameter difference is exactly 25 times, the area difference is 625 times. I think the one on the left looks more than 25 times bigger and has vastly more than 25 times as much detail.

But surely detail is determined by resolution not by size? The planet on the right obviously has as much detail as the planet on the left (they are both Jupiter) but the resolution of the image/scope/eyes/screen is not adequate to show it. It might look more than 25x bigger but as you say, it's not.

For argument's sake if we assume the rh image is what you would see in the scope at 50x, then the lh image shows what you would see at 1250x, in other words it's 25x bigger. The rh image would be 50x the diameter of what the unaided human eye would see if we could measure it. Basically, I think we are all agreeing?

[Stu]

19 minutes ago, Moonshane said:

But surely detail is determined by resolution not by size? The planet on the right obviously has as much detail as the planet on the left (they are both Jupiter) but the resolution of the image/scope/eyes/screen is not adequate to show it. It might look more than 25x bigger but as you say, it's not.

For argument's sake if we assume the rh image is what you would see in the scope at 50x, then the lh image shows what you would see at 1250x, in other words it's 25x bigger. The rh image would be 50x the diameter of what the unaided human eye would see if we could measure it. Basically, I think we are all agreeing?

I think I agree that we are all agreeing Shane ??

[cloudsweeper]

1 hour ago, Moonshane said:

But surely detail is determined by resolution not by size? The planet on the right obviously has as much detail as the planet on the left (they are both Jupiter) but the resolution of the image/scope/eyes/screen is not adequate to show it. It might look more than 25x bigger but as you say, it's not.

For argument's sake if we assume the rh image is what you would see in the scope at 50x, then the lh image shows what you would see at 1250x, in other words it's 25x bigger. The rh image would be 50x the diameter of what the unaided human eye would see if we could measure it. Basically, I think we are all agreeing?

Exactly - which is why max mag is limited by resolution.  Another example: think of how photos were once printed using dots.  When you up the mag too much, you just get bigger dots, but no more detail.

Doug.

[Stub Mandrel]

2 hours ago, Moonshane said:

But surely detail is determined by resolution not by size? The planet on the right obviously has as much detail as the planet on the left (they are both Jupiter) but the resolution of the image/scope/eyes/screen is not adequate to show it. It might look more than 25x bigger but as you say, it's not.

For argument's sake if we assume the rh image is what you would see in the scope at 50x, then the lh image shows what you would see at 1250x, in other words it's 25x bigger. The rh image would be 50x the diameter of what the unaided human eye would see if we could measure it. Basically, I think we are all agreeing?

Fair comment, but assuming the image was sharp (as it should be using a scope at 25x in decent seeing) then the resolution would be better both horizontally and vertically allowing 625 times as much detail to be seen. A better comparison using a sharp image. This should make it abundantly clear that magnifying by 25 diameters increases the amount of detail by vastly more than 25 times, assuming the image remains sharp:

[Moonshane]

Going back to the original question :

My question is just what is meant by magnification. If I look at, say, Jupiter with the unaided eye that I assume is 1x mag. Now if I use a 20mm eyepiece my understanding is that the magnification is 25x. However Jupiter certainly is not 25x larger and if I go to the 4mm eyepiece then |I should have 125x magnification or, I am assuming, that the image should be 5 times larger than that with the 20mm eyepiece but it most certainly is not.

The answer is simply, yes it is.

[Charic]

13 hours ago, Charic said:

The image produced by the telescope itself is real-time, real scale, 1-1.  

 

Ignore that line.

My telescope creates an image of a distant object, at the objective/mirrors focal point,  allowing me to look closer with the aid of an eyepiece, making the object look  bigger!

Now on my scope with  a focal length of 1200mm using a 6mm eyepiece  I can see a small image of Jupiter,  resulting  from 200x magnification, that is fact, but from the original post, Jupiter does not look 200x bigger?

I'm gonna stick with this theory for today 

This is what forums are for, and unfortunately  some folk (me)  sometimes go too deep to try and  better understand how it all works, but we will still have our own versions of how things work?

[Ricochet]

1 hour ago, Charic said:

200x magnification, that is fact, but from the original post, Jupiter does not look 200x bigger?

It is 200x bigger, but it is an optical illusion due to how your brain perceives the world that you overestimate the size of Jupiter in the sky and underestimate it through the telescope.

[LukeSkywatcher]

On 22/06/2016 at 13:57, Ricochet said:

It is 200x bigger, but it is an optical illusion due to how your brain perceives the world that you overestimate the size of Jupiter in the sky and underestimate it through the telescope.

I was wondering how long it would be before someone mentioned the words "optical illusion". I'm quite happy to go along with the above quote. So the words "larger/bigger/closer" are all correct. It just depends which one you prefer to use. I guess they really only come into play when talking about imaging?. For visual observing it matters not.

I'll stick with "closer". 

[peligroso]

I am blown away by all the discussions that have resulted from my original question. I need time to read them (and re-read them) in order to understand all the posts. Thank you all so much. It bodes well for this site that so many people have taken the trouble to pass on information. Again, thank you all so much

[Peter Drew]

Jupiter isn't really a very good candidate for this discussion because you can't actually see it with the naked eye, it's too small! What you can see, is the same as you see with stars, the light from them. The patch of light that you recognise as being Jupiter is just that, a patch of light. The true small disc of Jupiter when magnified 200x is not going to look 200x larger than the patch of light.