Hubble: Why It Can See Galaxies But Not That Moon Rock.

a reply to: wildespace

Very good point that I tried to cover at the end of my OP.

Things like Orion's Nebula and the Andromeda Galaxy, actually cover large sections of our sky, but their light is very faint and can be hard to see with just your eye. The telescope not only increases the resolution, but it is focusing the light, so in a way it's making it "brighter" for your eye to see.

If you look at a star chart (download Stellarium, it's 100 percent free and kept up to date), you'll see huge nebula that are in our skies, but you can't see well with just your eyes. Cameras can capture them, but only because we can make the camera take a picture for a long time (we can expose the frame for many seconds to hours), where as your eye can only "expose" a "frame" for about 1/5 of a second at it's longest...which is why we have horrible night vision, hehe.

S&F !
Awesome work you did there.
Now the Moon Landing folks will stop the chatter...nah

so you could see the moon landewr?
not a chance.........

originally posted by: wolfenz
I have said this many time's in many Thread's ....
as when you look at Some Galaxy Photo's from the 50s to Present Day ...


Those Stars you see in the Foreground " in front of the Galaxy" are more Likely Ours from Our Own Galaxy " Milky Way"


A 1950s Observatory Photo of a Cluster Nebula..

See those to Big Stars ... those are either from our Galaxy ( looking towards this Galaxy in the Photo )
or Close By Rouge Stars Obstructing the View

Another 1950s Observatory Photo

The One's Boxed in, are More Likely From Our Galaxy the Milky Way, or Rouge Stars " Orphaned "

The Original Photo

So there you have it, from Observatory Telescopes from the 1950s

With the Hubble Telescope .. We should see more Great Detail ! then a 1950s Photo
when The Hubble Captures Up in Close Stars ..

We Should be seeing Clear Objects , Stars to Planets of the Nearest Stars

In way Better Detail then we are Seeing them...

a reply to: wolfenz


We do see better images but you still have to consider how far away those foreground stars are.

a reply to: eriktheawful


I really appreciate the explanation. Because lately I have been wondering about this very issue myself. Do you know if the new telescope they're going to launch next will be any better at this issue than Hubble ?

a reply to: wolfenz

I'm afraid you still do not understand.

It's physically impossible for the Hubble Space Telescope, or even the largest ground telescope, to see anything of detail when it comes to another star even in our galaxy.

Even if the star in question is 1 million miles wide, if it were say 4 light years away, that puts it almost 24 TRILLION miles (24,000,000,000,000) away.

Even when something is a million miles wide, if it's that far away, it's angular diameter from Earth is going to be very small.

For example, Alpha Centauri A is just over 4 lightyears from us, but that is still so far away that it's angular diameter (how much of the sky it covers) is only 0.007 arcseconds.

Using the math in the OP, using Hubble with a 0.05 resolution, means that at that distance and size, something needs to be just over 7 million miles wide in order to Hubble to see any detail at all.

Alpha Centauri A is about 1 million miles wide, and even though it's only just over 4 light years away, it's just too small and too far for Hubble to see anything besides a point of light.

See planets that far using Hubble? No. Impossible. Hubble's primary mirror is way, way too small.

To even have a hope of actually seeing it, it would need to be a planet just over 7 million miles wide. That's over 7 times or more bigger than Alpha Centauri A itself, and don't even think about trying to see an Earth sized planet at that distance.

There are much bigger stars, and huge Jupiter exoplanets many times bigger. But many of these are tens, to hundreds and even THOUSANDS of light years away. They may be a LOT bigger, but then the other side of the math kicks in: They are just WAY to FAR.

If you want to see stars in detail, or catch even a glimps of a exoplanet, you're going to need a telescope who's primary mirror is measured in miles.

a reply to: Okeyd57

If it get's built, it would be able to see things as small as about 73 meters across on the Moon. The LROC we have in orbit about the Moon can see things on it down to 0.5 meters, so it would not be a huge improvement if you wanted to see very small objects on it.

It will be almost 3 times as the biggest telescope we have ever made, but it's still mostly looking at very large objects (nebula and galaxies) that are very far away.

Looking at things in our own solar system, it's still much easier to simply send a probe to it.

For seeing other planets around other stars: we need to build a massive telescope out in space. If you Google it, you'll find many plans and ideas for this. Problem for it mainly is money. Cost a lot to build something like that.

originally posted by: eriktheawful
If you want to see stars in detail, or catch even a glimps of a exoplanet, you're going to need a telescope who's primary mirror is measured in miles.

Are you aware that exoplanets, much farther away than Alpha Centauri, have been imaged?

If ya go to my observatory site, and navigate to the exoplanet database, then click on "pl_method" it will show you the list of planets discovered via "imaging"...

We are also able to "read" the atmosphere on many, predict the weather on a few...and of course, like I said, some have been "imaged".

ETA: by the way; I actually DO expect to "catch a glimps" of an exoplanet with my little telescope, though it will likely be through microlensing...but I do expect to catch that glimps and, get a "reading" on it's atmosphere...

originally posted by: eriktheawful
The Moon's diameter is 3476 kilometers. Its average distance from us is 384,000 kilometers. As I said above, a full moon covers about 1/2 a degree of our sky, or 1,800 arcseconds. Knowing this, and knowing both the size and distance of the moon, we can figure out what the smallest detail on the moon is that your eyes can see:

Take the diameter of the moon, 3476 km, and divide it by the amount of arcseconds a full moon covers, 1800 arcseconds, and you get 1.93, which is how many arcseconds 1 km is when seeing the moon from the Earth's surface. Now multiply that by the resolution of your eyeball, which is 60 arcseconds, and that means the smallest object your naked eye can see on the moon's surface is: 115.86 km wide.

So as you can see, it's not only the size of the aperture that matters, but also how big an object is AND how far away it is.

Why, prey tell, are you using the size of the remote object (moon)? The size of the object being observed is irrelevant to what the telescope can resolve.

Distance, now that is kind of important...and the angle defined by the Dawes limit.

You can easily determine what a telescope or other instrument can resolve by knowing it's Dawes limit, and the distance to the object. Then solving for the triangle defined by these two numbers.

In the case of Hubble...it turns out to be around 87 meters. And your arcsecond...1.6km.

originally posted by: eriktheawful
a reply to: wolfenz

I'm afraid you still do not understand.

It's physically impossible for the Hubble Space Telescope, or even the largest ground telescope, to see anything of detail when it comes to another star even in our galaxy.

Even if the star in question is 1 million miles wide, if it were say 4 light years away, that puts it almost 24 TRILLION miles (24,000,000,000,000) away.

Even when something is a million miles wide, if it's that far away, it's angular diameter from Earth is going to be very small.

For example, Alpha Centauri A is just over 4 lightyears from us, but that is still so far away that it's angular diameter (how much of the sky it covers) is only 0.007 arcseconds.

Using the math in the OP, using Hubble with a 0.05 resolution, means that at that distance and size, something needs to be just over 7 million miles wide in order to Hubble to see any detail at all.

Alpha Centauri A is about 1 million miles wide, and even though it's only just over 4 light years away, it's just too small and too far for Hubble to see anything besides a point of light.

See planets that far using Hubble? No. Impossible. Hubble's primary mirror is way, way too small.

To even have a hope of actually seeing it, it would need to be a planet just over 7 million miles wide. That's over 7 times or more bigger than Alpha Centauri A itself, and don't even think about trying to see an Earth sized planet at that distance.

There are much bigger stars, and huge Jupiter exoplanets many times bigger. But many of these are tens, to hundreds and even THOUSANDS of light years away. They may be a LOT bigger, but then the other side of the math kicks in: They are just WAY to FAR.

If you want to see stars in detail, or catch even a glimps of a exoplanet, you're going to need a telescope who's primary mirror is measured in miles.

you are failing to understand what Im getting at ,,

The Photos of Galaxy's Nebula's ETC... from Observatory's back in the 1950s and The Hubble Scope since the Early 1990s practically are theres no difference.. except in Color .. a Slight Atmospheric Difference from the Observatory ( until recently )

as Ill Put this Up Again

Ok Let's Do this Again! Shall WE



You See those TWO Big Stars, there from of this Galaxy those TWO Big Object's ( right of the Screen )

Those Stars are from the Outer Reach's of OUR Own Galaxy... you know , as the Milky Way..

In other word's, those Star's are in the Way of that Galaxy for a Photo Shoot

yet you can pretty much see the Detail of those two Stars also..

Yet The Hubble can NOT do any better ? Then a 1950s Observatory Technology.. ?? of seeing a Star that is ..

and What Galaxy is this that's in this Photo ! ???
Andromeda

...Wait !! what Trickery is this ...

They Do !! Show Better DETAIL!! ( Hubble )

SO MUCH that we are Seeing Close Detail's of Billions of Stars from another Galaxy ( Andromeda )

See Below !!

My God, It’s Full of Stars
7 January 2015/in Galaxies /by Brian Koberlein
briankoberlein.com...

Gigapixels of Andromeda [4K]
www.youtube.com...=52



YET, as i said if the Hubble can Do this !

Why are we not seeing Stars in our Own Galaxy in Great Detail .. as to MUCH !

We should at least See Planet's ( Caught going around its star ) in some of these Stars in OUR Neighborhood called Milky Way should we not from the Perspective of the Hubble Scope


this is what I'm trying to Explain HERE..


Did I know about this Gigapixel Video from the Hubble Scope ,,
yup I DID around FEB of this Year .. Amazing Work .. ( I can here the 2001 Space Odyssey Theme )

was there anything shown to the Public like this Discovery

yeah somewhat ... not as in Great Detail like this, years ago with the Hubble Scope


We Should See Something like this , for Planet Hunting at least

seeing we can see billion of Stars in The Andromeda Galaxy in Great Detail with The Hubble Scope..




So more Less of Everything you trying to explain your contradicting yourself ..

As you Said ...

It's physically impossible for the Hubble Space Telescope, or even the largest ground telescope, to see anything of detail when it comes to another star even in our galaxy.

Yet we can See Star's from another Galaxy in Great Detail
from the Hubble Scope but NOT our Own in the Outer Reaches ( Edges ) of our Galaxy ... OK got it ...

Alpha Centauri A is about 1 million miles wide, and even though it's only just over 4 light years away, it's just too small and too far for Hubble to see anything besides a point of light.

And ?? how far is the Andromeda Galaxy ?


Here is a Little Explanation

Why can Hubble get detailed views of distant galaxies but not of Pluto?

Posted by Emily Lakdawalla

2013/02/14 18:37 UTC
www.planetary.org...


Basically My View is the Hubble Scope is to Strong to see Pluto ..

I think it's more like "why do we have a telescope like Hubble in orbit to view galaxies but none to view that High Res moon rock".. Who cares who knows all about what already. We fund the damn projects! Why can we not see for our self!...

Well,,, this is Interesting ..

good to know


How Far Away Is It - 11 - Andromeda (1080p)
www.youtube.com...

a reply to: tanka418

Context. Size of the object you are trying to view does mater quite a bit.

Take Pluto. Hubble, as good as it's resolving power is, can not really give us any detail, not only because of how far away Pluto is, but because of it's small size.

Replace Pluto with Jupiter. It's over 88,000 miles wide. Features on the gas giant are large enough to where Hubble would be able to see the various cloud bands and even the Great Red Spot, because the size of those features are greater than the minimum size to see something at that distance.

Take Alpha Centauri A. It's about 1 million miles wide. At just over 4 light years, it's too far away for Hubble to see any details on it's surface (IE things like sun spots).
However, if we remove Alpha Centauri A and put in it's place say, Orion's Nebula, which is 12 lightyears wide (over 72 Trillion miles) we would certainly be able to see quite a LOT of detail in the nebula itself....all because the features of the nebula are quite large. (and it would be a heck of a view for us here on Earth, covering quite a bit of our night sky since it's width is wider than it would be far from us).

So yes, size of the object DOES mater. Hubble can see craters and mountains on the moon because many of them are kilometers in size, but at that distance, it can't see a 50 centimeter rock.

a reply to: tanka418

There is quite a bit of difference between detecting, and seeing.

We can detect a drop in light level of a star when something passes between it and us. If it does so on a regular schedule, showing a period, then it becomes obvious that it is an object in orbit around that star.

When the star light is examined when that object passes in front of it, yes, we can even tell if it has an atmosphere and what makes up that atmosphere.

But....

That is not the same thing as being able to optically see the object and resolve details of it's surface.

Please provide links to the images of these exoplanets that you say we are seeing. I would dearly love to see what they look like. What kind of contenents they have, oceans, craters, and for the gas giants, it would be wonderful to see their gas bands, etc.

To date: we do not have anything powerful enough to show us details of these object's surface features.

Please provide the links to the images that do show these details. I would be more than happy to be wrong about this.

too bad the hubble can't image the moon details it takes nice deep space pics though

a reply to: Wolfenz

I'm afraid you still do not understand the purpose of this thread.

You say you are seeing details of these stars.

I'm looking. I'm not seeing any sun spots nor any flares from them. Do those images show any surface details?

No, they do not.

Hubble is NOT one of the largest telescopes built. With a primary of 2.4 meters, is quite small compared to many telescopes here on Earth.

In 1917, on Mount Wilson, the Hooker telescope was built with a 100 inch or 2.5 meter primary mirror. That's bigger than Hubble.
In 1948, they built yet a bigger telescope at the Palomar Observatory, a whopping 200 inch or 5.08 meter telescope.

We have telescopes now who's primary mirrors are HUGE, over 10 meters!

Hubble wasn't put into orbit because it was so big, it would be able to see huge detail. That wasn't the idea behind it.

Hubble was put into space because:

It's a large telescope that would no longer have to worry about the atmosphere. Starlight has to go through all of our atmosphere before a telescopes mirror can collect it. Hubble didn't have to worry about that.
Also it's orbit at 342 to 345 mile above the Earth allows it to look all around, where a Telescope in the northern hemisphere will see less and less of the southern hemisphere's sky the further north the telescope is, an the opposite is true for telescopes in the southern hemisphere.
Hubble doesn't have that issue.

The whole idea was to get a large telescope out into space, so it would not be affected by the Earth's atmosphere. And back in 1990 when it was placed there, that was very important.
Now, in today's world, we have very large telescopes who's primary mirrors are made up of many different mirrors that are controlled by computers to counter the effects of the atmosphere.

Why is that atmosphere all that important? Because it can affect the light coming in, making it very hard to see very faint deep space objects. That was Hubble's main purpose in life.

My OP isn't a theory as to why Hubble can't see the surface of Pluto, or that 2 foot wide rock on the Moon. My OP is based on the Law of Optics.

Not theory. Actual physical laws of how optics behave.

It's not that Hubble is "too strong".

It's because even Hubble has to follow the same optical laws as any telescope. It simply can not see a very small object from that far away.

Even the 30 meter telescope if they get it built will not be able to see a 2 foot rock on the moon.

Nor will it be able to see sun spots on Alpha Centauri A. They're too small and too far away.

a reply to: Corruptedstructure

If you read the op YOU wouldn't ask such a stupid question.

a reply to: Wolfenz

The 2 fuzzy objects in the Andromeda picture are not stars they sre dwarf Galaxies do a Google search for Andromeda dwarf Galaxies.