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WSTAR - Small Radio Telescope

In order for UW undergraduates to gain experience with interferometry, the junior members of the ObsCosLab began a project to build three Small Radio Telescopes (SRTs) to map the neutral Hydrogen of the Milky Way.

21 cm Emission Lines

Neutral Hydrogen consists of one proton and one electron. When the spins of the proton and electron are aligned the atom has a slightly higher energy than when the spins are opposite. When an electron in the lowest orbital changes from spin aligned to misaligned the energy of the atom decreases by a small energy E. In order to conserve energy, the a photon must be emitted with frequency f=E/h=1420 MHz, corresponding to a wavelenght of 21cm. Our radio telescopes are designed to be sensitive to a small band of frequencies centered at 1420 MHz.

Unlike a single telescope, an interferometer combines the signals from an array of telescopes to obtain measurements with much higher resolution. A typical interferometer, a "multiplying interferometer," nominally consists of receivers, pre-amplifiers, and a correlator that multiplies the signals together.

We Used the Documentation and Program from MIT Haystack, MA. Their webpage is and the srt page is


 WSTAR group






Last updated: 7/20/10

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