Why are Radio Telescopes less detailed?

[Vorde]

In my experience pictures from radio antennae are far less accurate than pictures from other areas of the EMR spectrum, why is this?

 

[twofish-quant]

In my experience pictures from radio antennae are far less accurate than pictures from other areas of the EMR spectrum, why is this?

For single telescopes the issue is diffraction limits. The minimum resolution that you can see is on the order of (wavelength) / (telescope size), and since radio telescopes have long wavelengths, you get less resolution.

The other issue is that radio waves often come from objects that are more diffuse.

Now things are very different for VLBI. With VLBI you use the rotation of the Earth and computers to create an artificial telescope that can be the size of the earth. In that situation, you can get pictures that are much more detailed than you have in visible.

 

[DaveC426913]

Now things are very different for VLBI. With VLBI you use the rotation of the Earth and computers to create an artificial telescope that can be the size of the earth. In that situation, you can get pictures that are much more detailed than you have in visible.

Why does the principle behind VBLI work for radio but not for visible?

I'm thinking it has something to do with the "I"...

 

[Chronos]

twofish is correct, it has to do with wavelength. A radio telescope 'lens' is need only be corrected to within a few millimeters. That is why they can be made so large.

 

[twofish-quant]

Why does the principle behind VBLI work for radio but not for visible?

Because with radio waves you can see the actual shape of the "wave". You can track exactly when the peak of the wave hits the Earth which is going to be different for different parts of the earth. Once you synchronize these measurements with an atomic clock, you can work back and electronically reconstruct the wave as it hits the earth.

For light, you can't record phase information, so you have to physically combine light rays. This means that you can't build an artificial telescope the size of the earth.

 

[DrStupid]

Why does the principle behind VBLI work for radio but not for visible?

It works: http://www.eso.org/sci/facilities/paranal/telescopes/vlti/