"Crude" satelite timing

From: pmorini@libero.it
Date: Mon Feb 03 2003 - 06:11:27 EST

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    In my wandering in old publications, I got the sept/oct 1961 issue of 
    "Coelum" an astronomy magazine published in Italy by the Bologna 
    astronomical observatory.
    I found an article in which was suggested to time the eclipse of the 
    satellite caused by the shadow of the Earth.
    To take in account the movement of about 1 deg/day of the umbral cone of 
    the earth, for satellite with a period of about 2 hours and moving in 
    direct mode (the article was dealing with Echo 1 sat), the suggestion is 
    to subtract 2 sec per revolution.
    The timing over 1 year gives for Echo sat the period decreasing from 
    118.28 min (31 aug 1960) to 116.9 min (15 aug 1961).
    I'd like to perform on my own such an observation.
    A big advantage is that you have not to build any instrument - need only 
    a binoculars and stopwatch.
     From observing satellite vanishing in the earth shadow, I guess you can 
    time the swicth-off-time with an approximantion of some seconds, the 
    observation program on a single satellite must be run for, say, 1 year 
    at least.
    Probably it would be better to deal with circular orbit satellites (to 
    neglect the variation af the argument of perigee) of known inclination 
    (to calculate the time difference of the eclipsing time in second/orbit 
    due to westward precession and earth revolution).
    Some suggestions about ?
    Probably I can simulate the activity with my Satspy software, to plan 
    the observing sessions during the year.
    The sake of the game ? To "touch" the space from my backyard ...
       Paolo Morini
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