Compare the highest resolution attainable with optical telescopes with the highest resolution attainable with?

Question

Compare the highest resolution attainable with optical telescopes with the highest resolution attainable with radio telescopes (including interferometers)

Answer 1

The smallest ANGULAR resolution (alpha) is given by Rayleigh's formula:

alpha = 1.22 (lambda / D).....where lambda is the wavelength of the radiation and D is the diameter of the objective.

So you can see for the longer wavelengths of radio waves the angular resolution is much worse UNLESS you increase D, the size of the objective significantly.

Answer 2

The highest resolution is directly proportional to the wavelength of the radiation you're observing. Take the wavelength of visible light to be about 500 nm and radio emissions to be the 21cm. neutral hydrogen wavelength. Then the finest detail you can observe with a radio telescope is about 400 000 times as coarse as with an optical one of the same size. But the biggest radio telescope dish is about 1 km. diameter; the Arecibo dish. The biggest optical telescope aperture is about 600 cm. That's a ratio of about 150. So divide 400000 by 150 to get about 2500 as your ratio. The best resolution you can get with an optical telescope is about 0.001 arcsecond. If you use arrays of either optical or radio telescopes you can get better resolutions with both. The diameter of the array counts as the aperture. In the case of optical scopes I haven't allowed for atmospheric turbulence reducing the resolution of an Earth-based scope. If there's a planet like Earth circling Alpha Centauri, 4 1/2 light years away, an array of optical telescopes 5 million km across in Earth orbit would show its continents with a resolution of about 4 km.

Answer 3

Resolution is ultimately a function of wavelength. An optical telescope will have 1000X the resolution of a radio telescope due to visible light wavelenghts being 1000X shorter than that of a radio telescope.

Many complicating factors from an ideal situation though. Radio telescopes can see through matter that would otherwise be opaque to a visible light telescope, so in this case, the Radiotelescope would have infinitly greater resolution than would a vis wavelenght scope.

Astrobuf

Answer 4

Yes astrobuf, except that they are now applying the principles of interferometry to optical telescopes.

Imagine two 10 m telescopes, separated by 85 m.
This gives a resolution of 5 milli-arcseconds (0.005") in red light, which rivals the resolution of Earth-sized Very Large Baseline Interferometers in radio.