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From: bie@solman.mlb.semi.harris.com (Ben Eaton)
Newsgroups: sci.electronics
Subject: RE: How to tell distance of Stars
Message-ID: <1991May16.191838.2265@mlb.semi.harris.com>
Date: 16 May 91 19:18:38 GMT
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        If memory serves me correctly there are three common methods used to 
     determine the distance to individual stars.

          A)   PARALLAX

                  In this method you measure the apparent shift in position 
               of a star in relation to other background stars as the earth 
               moves around the sun.  This method is only good out to about 
               one to two hundred light years.

          B)   COLOR VERSUS LUMINOSITY

                  In this method you measure the apparent luminosity of a 
               star and compare it to a star of the same color with a known 
               distance and use the inverse square law to calculate the 
               distance.  This works within our own galaxy but outside of 
               that I don't know.

          C)   PERIOD VERSUS LUMINOSITY

                  This method only works for variable stars and is just 
               like the color versus luminosity method only you compare 
               stars of like periods.  This works for as far out as you can 
               see the individual star.

        I hope this will be of some help if you want more get in contact 
     with a community collage that has an astronomy department.

     Ben