Is it possible for amateurs to do optical interferometry? (Intermediate)

I'm a keen amateur astronomer and member of a local club. I know basically what Optical Interferometry is (combining the signal of two or more telescopes to synthesize a larger scope) but can't find any technical details on how it is achieved. Is it all about software to synchronize two mounts and again to combine the images so they perfectly match? Is it possible for an amateur or two to get an optical interferometer up and running if they had computer knowledge (and enough savings!)?

Interferometry is MUCH more complicated than you think. You need a precise path length difference between the two interfering waves so that a good interference pattern is achieved. In Keck, there are a whole set of mirrors below the two observatories, and the mirrors can be adjusted to get the exact phase lag. It requires hardware and not mere computing power to do interferometry.

Further, as the object moves in the sky due to Earth's rotation, the fringe pattern will change due to the change in the phase difference. Usually, interferometers will have devices so that the central fringe is tracked by changing the path length of one of the beams. One of the problems with optical interferometry is that the wavelengths are very small, so that one is talking of doing things very precisely. Further, it is not a trivial business to recover information from the interference fringes (assuming that you do get a good interference pattern). Even in the radio, where interferometry is used extensively, extracting information from the observed fringes takes a lot of work.

So, interferometry is not as simple as taking two images from telescopes and combining them. For example, refer to the article, "A Sharper View of the Stars" by Arsen R. Hajian and J. Thomas Armstrong in the March 2001 issue of Scientific American (not currently available on their webpage, unfortunately), for a schematic diagram as to how optical interferometry may be done.

About the Author

Jagadheep D. Pandian

Jagadheep D. Pandian

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.

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