John Schutkeker wrote:
(Greg Hennessy) wrote in news:d17vv2$in5$1
@tantalus.no-ip.org:

If someone can repeat the question (I only see replies, not the head
article) I can try to answer the question. I am an employee of USNO.

I wanted to build an optical imaging interferometer that worked over a
phone line.

Why? What makes you think you would *ever* see any fringes?

BTW A single interferometer pair cannot form an image. So your claimed
objective is impossible or an oxymoron. You need a several different
baselines and a range of PA angles to stand any chance of forming even a
primitive image from interferometer data. Look up aperture synthesis
radio telescopes for more information at much easier wavelengths.

State of the art research optical interferometers like COAST use
relatively modest path lengths and devious path compensation measures in
climate controlled bunkers. I am unsure what the longest optical
interferometry baseline to see useful fringes is to date but I would be
surprised if it was more than 500m (the longest working optical baseline
I know of is 330m at CHARA).

ADS abstracts has some of the technical details online. Try the JPL
OLBIN coordinating site for an explanation of what you are up against:

http://olbin.jpl.nasa.gov/intro/

Regards,
Martin Brown