RE: Some errors in Heavens Above's prediction on Iridium Flares

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Wed Jul 31 2002 - 21:04:38 EDT

  • Next message: Tom Wagner: "Re: Some errors in Heavens Above's prediction on Iridium Flares"

    Hi Shea,
    
    > Recently, I've found something wrong in Heavens Above's prediction
    > on Iridium Flares. ... Most of them are right, but the Alt. is
    > wrong. The observation is that Alt. is nearly 90 [versus 60
    > observed]. The error is roughly 30, so great!
    
    You may be surprised at just how high in the sky the zenith
    really is -- it is not a comfortable direction to be looking
    while standing, and consequently most beginning observers
    overestimate all elevation angles -- with increasing errors
    as the angle increases.  Here is a typical altitude angle
    conversion table I use for "translating" beginners' reported
    altitude angles:
    
    Reported  Actual
      Angle    Angle
    --------  ------
        10       7
        15      10
        30      20 
        45      30
        60      45
        80      60
        90      70
    
    Try testing yourself with some bright stars that are well above
    the horizon -- guess their altitude angles and then use one
    of the many planetarium programs out there to see how close
    you were.  You may be surprised by the results.
    
    Best wishes,
    Rob
    
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