Telescope Resolution: Max Res with Pieced Mirrors?

[Drakkith]

Hey all. I know that the maximum resolution of a telescope directly relates to the size of the aperture and the wavelength of the light. What I'm wondering is what would happen if you took "pieces" of a much larger mirror from opposite edges and just used those pieces. Pretty much what this shows: http://en.wikipedia.org/wiki/File:Interf_diagram.gif

Would the resolution still be the same or not? I've read that it does, however my gut tells me that it's rarely as simple as putting a couple of mirrors together.

 

[davenn]

as long as those 2 pieces are still the same distance apart as when they were part of the same larger mirror then yes you would have higher resolution.
This is how the Keck twin scopes on Mauna Kea work. 2 x 10 metre scopes 85 metres apart. They give the resolution of a single mirror 85 metres in diameter.

Now the tradeoff tho, in what you suggested and the Keck twins is that you don't have the same light gathering power as say your smaller mirror that you have taken a section off each side or of the Kecks that you don't have the light gathering power of a 85metre diameter mirror. You ONLY have the equivilent resolution.

The same principle is used in radio astronomy like the VLA in New Mexico where they can contract or spread out the individual dishes along the rail tracks.

I went to the top of Mauna Kea in 1999 and visited the Keck's and a couple of the other scopes up there. pretty awesome :)
Half way up the road to the top is a radio telescope that is linked with one in the Andes mountains in Sth America. It gives a baseline of 1000's of kms awesome resolution at radio wavelengths.

The other thing that can be done with radio telescopes ( not sure about optical scopes) is you can take reading on a deep space object say today. then in 6 months time do the same again, intergrate the data and you have the resolution of a telescope with the diameter of the orbit of the Earth around the sun!. Now that's serious resolution abilities.

cheers
Dave

 

[Drakkith]

Thanks Dave! I'm hoping to be able to visit Mauna Kea one day myself.

 

[litup]

One caveat about multiple mirrors is they are still on Earth and you can get rid of a lot of atmospheric distortion with adaptive optics, it is so far still a very small field of view. Still better than Hubble in its tiny field. Hubble still has a leg up on wavelength though, a big slice of wavelengths it can see that doesn't make it through the atmosphere so it can still take images they can't see underneath our 100 miles of air.

 

[Drakkith]

I'm assuming the Michelson Stellar Interferometer acheives the same effect?
http://en.wikipedia.org/wiki/Michelson_stellar_interferometer

 

[Oldfart]

The other thing that can be done with radio telescopes ( not sure about optical scopes) is you can take reading on a deep space object say today. then in 6 months time do the same again, intergrate the data and you have the resolution of a telescope with the diameter of the orbit of the Earth around the sun!. Now that's serious resolution abilities.

Anyone know if this can (or will) be done with optical scopes?

In my dreamworld, I'd like to be able to optically scan the surfaces of the planets of distant stars to search for signs of life. Sounds tricky, assuming that the planet is rotating and the pictures are taken six months apart. A better way might be putting the whole interferometer in space, take a snapshot, dunno... Any thoughts?

 

[Chronos]

I would be happy with an adaptive optics system that would allow my 3 backyard scopes to function as one 100 meter scope.

 

[Drakkith]

I would be happy with an adaptive optics system that would allow my 3 backyard scopes to function as one 100 meter scope.

I'd be happy for a freaking filter wheel that doesn't decide to move filters on me even though:
A. It's got a broken wire in the connector which I thought was keeping it from even being powered on.
B. I didn't even have the filter wheel selected as an accessory in my program.

Three hours of 10 min subs on M101 and it looks horrible. I don't even know if it was the clear filter, red filter, or HA filter.

 

[davenn]

... Three hours of 10 min subs on M101 and it looks horrible. I don't even know if it was the clear filter, red filter, or HA filter.

crap, that's a pain in the tush !
But at least you have been able to use your scope. Since my new one arrived 2 weeks ago
we have had 1.5 weeks of cloud and rain and its set to continue for at least this coming week :(

A.S.D is setting in haha ( Astronomy Deprivation Sydnrome)
cheers
Dave

 

[Fozzie]

as long as those 2 pieces are still the same distance apart as when they were part of the same larger mirror then yes you would have higher resolution.
This is how the Keck twin scopes on Mauna Kea work. 2 x 10 metre scopes 85 metres apart. They give the resolution of a single mirror 85 metres in diameter.

So why didn't they build the telescopes further apart?

 

[Drakkith]

So why didn't they build the telescopes further apart?

For two separate telescopes they have to guide the light exceedingly precisely through vacuum tubes and off of mirrors and other optical equipment. The larger the distance between the two, the harder and more expensive all that is. Also, there may have been space issues with siting the telescopes, as there is only so far you can go until you are at the edge of the mountain or somewhere else not suitable for building a telescope.

 

[Oldfart]

For two separate telescopes they have to guide the light exceedingly precisely through vacuum tubes and off of mirrors and other optical equipment. The larger the distance between the two, the harder and more expensive all that is. Also, there may have been space issues with siting the telescopes, as there is only so far you can go until you are at the edge of the mountain or somewhere else not suitable for building a telescope.

Any hope for coupling the optical scopes electronically and letting a computer figure things out?

 

[Drakkith]

Any hope for coupling the optical scopes electronically and letting a computer figure things out?

Not yet, we don't have a way of measuring the phase of visible light. The frequency, in the terahertz range, is much too high. That is my understanding of why we cannot at least. 1 terahertz is 1 trillion hertz.

 

[Oldfart]

Drakkith -- Thanks much for the info! OF

 

[Drakkith]

If it is as simple as taking a couple of mirrors and placing them far apart, why are a lot of the planned observatories using absolutely massive mirrors? Just for the light gathering? Why not take two 1 meter mirrors, place them on a long arm 100 meters apart and do it that way? Seems like a MUCH cheaper solution. I feel like I'm missing a key piece unless the reason is just because these 10+ meter mirrors have much greater light gathering capability.

 

[davenn]

Hey Drakkith

the size of the mirror is for the light gathering, the distance apart, as in the 2 Kecks, is for the resolution. eg. a 10 metre diameter mirror has the same resolution as 2 x 1 metre mirrors 10 metres apart, but it has much more light gathering power, because of the bigger surface area.

cheers
Dave