[time-nuts] Re Danjon Astrolabe

Hal Murray hmurray at suespammers.org
Wed Sep 27 02:59:51 EDT 2006


> I wonder if it is possible to use radio astronomy. You'd have to find
> an object that doesn't require a very large antenna to acquire its
> signal. 

> I understand that optical tracking of a star crossing a hair is more
> precise than the peak of a radio signal, but perhaps modern signal
> processing would fix that. 

I don't know of much amateur radio astronomy work.

I'm far from a wizard, but all the antenna patterns that I'm familiar with 
have a central peak that's sin(x)/x.  That's got a flat top so it's real hard 
to find the center accurately.  I don't see how signal processing is going to 
help that.

The width of the peak is the inverse of the diameter of your antenna 
(measured in wavelengths).  I should be able to work out the math, but it 
would take some digging.  It's the same math as diffraction limited optics.  
I'm sure it's in Feynman.

If you want a time sink, you could use two antennas.  It might be fun, but I 
doubt if it's a practical way to get time.  The width of the central peak 
comes from the width (aka separation) of the pair.  But there are aliases 
next to it.  (No free lunch.)

How big is your back yard?

Do you have a friend down the street?  Do you have synchronized clocks?



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